{ "data": { "a": { "slug": "inworld-realtime", "name": "Inworld Realtime API", "vendor": "Inworld AI", "vendorUrl": "https://inworld.ai", "kind": "http-api", "category": "voice-agents", "summary": "Inworld's Realtime API runs spoken conversations over WebSocket or WebRTC, chaining Inworld STT, an LLM chosen by the developer and Inworld TTS, with turn detection, interruptions and tool calling. It follows OpenAI's Realtime protocol.", "url": "https://www.anchorterminal.com/tools/inworld-realtime", "markdownUrl": "https://www.anchorterminal.com/tools/inworld-realtime.md", "slimMarkdownUrl": "https://www.anchorterminal.com/tools/inworld-realtime.min.md", "jsonUrl": "https://www.anchorterminal.com/api/v1/tools/inworld-realtime.json", "dns": "inworld-realtime.grade.anchorterminal.com", "transports": [ "websocket", "http" ], "packages": [ { "registry": "npm", "name": "@inworld/cli" } ], "auth": "api-key", "authNotes": "Servers send `Authorization: Basic` with the Base64 `key_id:secret` credential. Browsers send `Authorization: Bearer` with a session token minted server side. The `key` query parameter in the WebSocket URL is a session ID, not a secret.", "pricing": "usage", "pricingNotes": "No per-minute or per-session price. A session is billed as its STT ($0.10 to $0.15 an hour), its LLM tokens at the model's rate and its TTS characters (TTS-2 from $25 per million on the free plan). Segments already sent to TTS are billed after an interruption.", "priceSummary": "Pay per use", "where": "local", "x402": { "level": "no", "evidence": "No x402, MPP or L402 in the docs, llms.txt or pricing page (checked 2026-11-06). Plans and credits are bought in the Portal.", "endpoints": [] }, "toolCount": 0, "popularity": { "githubStars": null, "npmWeekly": null, "pypiWeekly": null, "asOf": "2026-11-06" }, "docsUrl": "https://docs.inworld.ai/realtime/overview", "llmsTxt": "https://docs.inworld.ai/llms.txt", "capabilities": [ "voice.agent", "voice.pipeline", "voice.tools", "voice.telephony" ], "tags": [ "hosted", "usage", "free-tier", "closed-source", "llms-txt", "streaming", "websocket", "webrtc", "openai-compatible", "enterprise" ], "lastRelease": "2026-10-16", "graded": true, "anchor": { "graded": true, "score": 60.1, "grade": "C", "agentReady": false, "rank": 671, "ranked": true, "rankOf": 1510, "categoryRank": 12, "methodology": "0.7", "run": "2026-10-01", "scores": { "ergonomics": 68, "maintenance": 71, "payments": 40, "reliability": 62, "schema": 60, "security": 58, "transparency": 63 }, "pending": [ "performance", "tasks" ], "assessment": { "confidence": "medium", "date": "2026-11-06" }, "negative": 0, "verdict": "Inworld's Realtime API speaks OpenAI's Realtime protocol over WebSocket or WebRTC, with a choice of LLM, client-side tools and dated release notes. Cost is the sum of STT, LLM and TTS usage with no per-minute price, there is no machine-readable event schema, and status history couldn't be read.", "bestFor": "Teams moving off OpenAI's Realtime API who want a choice of LLM and Inworld voices.", "strengths": [ "Follows OpenAI's Realtime events, with a migration guide that changes only the URL, key and a few defaults", "Dated release notes name affected clients and required actions for each compatibility change", "A choice of LLM through Inworld's router, with prompt caching on Anthropic models", "Concurrent sessions from 10 on the free plan to 1,000 on Growth", "Zero data retention covers session content from the Developer plan up" ], "weaknesses": [ "No per-minute price. A session's cost depends on STT, LLM tokens and TTS characters, and interrupted segments are still billed", "No AsyncAPI or other machine-readable schema for the socket events", "Status history couldn't be read, and an SLA exists only for Enterprise", "The 21 July 2026 release changed response and item shapes for existing clients", "Zero data retention doesn't cover requests routed to third-party LLM providers" ], "agentNotes": [ "Set the auto follow-up off if your client sends its own `response.create` after a tool result, or replies double", "Read `response.done` usage as an estimate and mute input audio when nobody speaks, since STT bills every second sent", "Use `response.speak` for fixed greetings, which skips the LLM", "Treat `unsupported_field` errors as warnings and keep the session open", "Mint browser session tokens on your server and never ship the Basic credential to a client" ], "metrics": { "kind": "remote", "measured": false }, "reviewCount": 0, "avgRating": 0, "history": [ { "basis": "public evidence", "confidence": "medium", "grade": "C", "methodology": "0.7", "pending": [ "performance", "tasks" ], "run": "2026-10-01", "runLabel": "October 2026 research run", "score": 60.1 } ], "editorialScores": { "ergonomics": 68, "maintenance": 71, "payments": 40, "reliability": 62, "schema": 60, "security": 58, "transparency": 51 }, "provenanceScore": 75, "checked": { "categories": { "ergonomics": "2026-11-06", "maintenance": "2026-11-06", "payments": "2026-11-06", "reliability": "2026-11-06", "schema": "2026-11-06", "security": "2026-11-06", "transparency": "2026-11-06" }, "last": "2026-11-06", "oldest": "2026-11-06", "stale": false, "staleAfterDays": 90 } }, "connect": { "install": "npm install -g @inworld/cli" }, "letme": { "capability": "https://letme.dev/voice.agent", "tool": "https://letme.dev/inworld-realtime" }, "sameCompany": [ "inworld-stt", "inworld-tts", "inworld-voice-cloning" ], "area": "voice", "unitPrices": [ { "item": "Speech recognition in a session", "unit": "audio-minute", "usd": 0.0025, "note": "STT-1 at $0.15 an hour On-Demand, $0.10 on paid plans" }, { "item": "Agent speech, TTS-2", "unit": "1m-chars", "usd": 25, "note": "free On-Demand plan; lower on paid plans" } ], "provenance": { "legalEntity": "Theai, Inc. dba Inworld AI", "domain": "inworld.ai", "domainRegistered": "", "endpointOnVendorDomain": true, "terms": "https://inworld.ai/terms", "privacy": "https://inworld.ai/privacy", "statusPage": "https://status.inworld.ai", "changelog": "https://docs.inworld.ai/release-notes/realtime", "securityTxt": "none", "checked": "2026-11-06", "notes": [ "The Terms of Service (effective 11 June 2025) are an agreement with Theai, Inc. dba Inworld AI under California law, with courts in Santa Clara. The Privacy Notice (last updated 18 January 2026) names Theai, Inc.", "inworld.ai/.well-known/security.txt returns 404. The security page links a vulnerability report form.", "status.inworld.ai runs the open-source issue-status app, which draws incidents from GitHub issues in inworld-ai/inworld-issue-status. Its history wasn't read, because GitHub's robots.txt couldn't be read from our environment.", "inworld.ai's robots.txt allows Claude agents on the paths read and sets `Content-Signal: ai-train=no, search=yes, ai-input=no`. docs.inworld.ai has no such signal.", "The domain's registration date wasn't established, because the RDAP lookup failed.", "firstReleased is left empty. The public Realtime release notes start on 21 July 2026 and no launch date was found." ], "score": 75 }, "pageJsonUrl": "https://www.anchorterminal.com/tools/inworld-realtime.json", "live": { "slug": "inworld-realtime", "vendorStatus": { "page": "https://status.inworld.ai", "indicator": "unknown", "summary": "no machine-readable status found", "checkedAt": "2026-11-07T04:47:57.03709454Z" }, "versions": [ { "registry": "npm", "name": "@inworld/cli", "version": "1.5.0", "seenAt": "2026-11-06T23:35:04.551623033Z" } ], "npmWeekly": 290, "securityTxt": { "url": "https://inworld.ai/.well-known/security.txt", "state": "none", "checkedAt": "2026-11-07T16:01:11.794771951Z" }, "llmsTxt": { "url": "https://docs.inworld.ai/llms.txt", "ok": true, "status": 200, "checkedAt": "2026-11-07T15:32:46.028273902Z" }, "pages": [ { "url": "https://docs.inworld.ai/release-notes/realtime", "kind": "changelog", "status": 200, "checkedAt": "2026-11-07T14:06:42.218731652Z", "changedAt": "0001-01-01T00:00:00Z", "fingerprint": "9ae0f1f05b69" }, { "url": "https://inworld.ai/privacy", "kind": "privacy", "status": 304, "checkedAt": "2026-11-07T14:11:39.031139211Z", "changedAt": "0001-01-01T00:00:00Z", "fingerprint": "99dc39a9de92" }, { "url": "https://inworld.ai/terms", "kind": "terms", "status": 304, "checkedAt": "2026-11-07T14:11:41.181276356Z", "changedAt": "0001-01-01T00:00:00Z", "fingerprint": "777d881cbf9b" } ], "updatedAt": "2026-11-07T16:01:11.794771951Z" } }, "answer": "Vapi API + MCP scores 64.7 (B) on agent readiness against Inworld Realtime API's 60.1 (C), and leads in 5 of 7 scored categories. Inworld Realtime API leads on payments \u0026 pricing.", "b": { "slug": "vapi", "name": "Vapi API + MCP", "vendor": "Vapi", "vendorUrl": "https://vapi.ai", "kind": "http-api", "category": "voice-agents", "summary": "Developer platform for phone and web voice agents.", "url": "https://www.anchorterminal.com/tools/vapi", "markdownUrl": "https://www.anchorterminal.com/tools/vapi.md", "slimMarkdownUrl": "https://www.anchorterminal.com/tools/vapi.min.md", "jsonUrl": "https://www.anchorterminal.com/api/v1/tools/vapi.json", "dns": "vapi.grade.anchorterminal.com", "repo": "https://github.com/VapiAI/mcp-server", "license": "MIT (MCP server)", "transports": [ "http", "streamable-http", "stdio" ], "remoteUrl": "https://api.vapi.ai", "packages": [ { "registry": "npm", "name": "@vapi-ai/server-sdk" }, { "registry": "npm", "name": "@vapi-ai/web" }, { "registry": "pypi", "name": "vapi_server_sdk" }, { "registry": "npm", "name": "@vapi-ai/mcp-server" } ], "auth": "api-key", "authNotes": "Private API key as a bearer token for the REST API and the hosted MCP server at `https://mcp.vapi.ai/mcp` (an SSE endpoint also exists). A separate public key is for browser calls with the Web SDK. The local MCP server reads `VAPI_TOKEN`.", "pricing": "usage", "pricingNotes": "Usage only is $0.05 a minute Vapi hosting, plus transcriber, model, voice and telephony at provider cost, prepaid with $5 of free credits to start. Vapi telephony, SIP, WebSockets and WebRTC transport are free, Twilio inbound runs $0.008 a minute and outbound $0.014. Success Packages add support and limits on top of usage, Core $29 a month and Pro 10 per cent of the hosting fee with a $999 monthly minimum. Add-ons include HIPAA at $2,000 a month and extra concurrent lines at $10 a line a month. The vendor's calculator puts 1,000 minutes with Deepgram, OpenAI and ElevenLabs at roughly $0.08 to $0.13 a minute all in (https://vapi.ai/pricing).", "priceSummary": "$29 / mo", "where": "both", "x402": { "level": "no", "evidence": "No x402 support in the docs, pricing page or MCP docs (checked 2026-09-30).", "endpoints": [] }, "toolCount": 13, "popularity": { "githubStars": 57, "npmWeekly": 177088, "pypiWeekly": 42248, "asOf": "2026-09-30" }, "docsUrl": "https://docs.vapi.ai", "llmsTxt": "https://docs.vapi.ai/llms.txt", "openapi": "https://docs.vapi.ai/openapi/api-reference.json", "capabilities": [ "voice.agent", "voice.pipeline", "voice.speech-to-speech", "voice.tools", "voice.telephony" ], "tags": [ "hosted", "closed-source", "no-card", "mcp", "llms-txt", "openapi", "typescript", "python", "webhooks", "streaming", "pipeline", "speech-to-speech", "enterprise" ], "lastRelease": "2026-10-30", "graded": true, "anchor": { "graded": true, "score": 64.7, "grade": "B", "agentReady": false, "rank": 459, "ranked": true, "rankOf": 1510, "categoryRank": 10, "methodology": "0.7", "run": "2026-10-01", "scores": { "ergonomics": 67, "maintenance": 88, "payments": 35, "reliability": 70, "schema": 89, "security": 61, "transparency": 75 }, "pending": [ "performance", "tasks" ], "assessment": { "confidence": "medium", "date": "2026-11-02" }, "negative": -4, "negativeNotes": [ "2026-06-03. A compromised developer GitHub token was used to push malicious code to Vapi repositories and publish four malicious `@vapi-ai/server-sdk` versions (0.11.1, 0.11.2, 1.2.1, 1.2.2) to npm. Vapi says they were removed within about three hours with zero downloads and no customer data exposed, and it published a write-up. Fixed and documented, so we deduct 4 of a possible 15 (https://vapi.ai/blog/our-response-to-june-3-supply-chain-incident)." ], "verdict": "Voice agents can combine supported transcription, model and voice providers, including customer-supplied endpoints, with a weekly changelog and an OpenAPI file. Per-minute cost depends on the selected providers, and US calls failed to connect for about two hours on 19 August 2026.", "bestFor": "Developers who want to choose every provider, bring their own keys and tune cost against latency.", "strengths": [ "Any mix of transcriber, model and voice provider, or your own keys and endpoints", "OpenAPI file with 145 operations, llms.txt and a weekly changelog", "Public keys limited to allowed origins and assistants", "99 per cent uptime SLA on the Pro package, 99.9 per cent on Premier", "Versioned assistants and tools with draft, publish and traffic splitting" ], "weaknesses": [ "Real per-minute cost depends on provider choices", "Usage only has 4 concurrent lines and 14 days of retention", "The MCP server's `create_call` places real calls with no annotation", "No request rate limits, Retry-After or idempotency keys for calls found", "Malicious SDK versions reached npm for about three hours on 3 June 2026" ], "agentNotes": [ "Read `subscriptionLimits.concurrencyBlocked` in the `POST /call` response, a full account queues the call rather than failing", "Confirm with a person before `create_call` through the MCP server, the server won't ask", "Pin transcriber, model and voice and set fallback plans so one provider outage doesn't drop calls", "Read the call log's cost breakdown to see what each provider charged", "Check `@vapi-ai/server-sdk` isn't pinned to 0.11.1, 0.11.2, 1.2.1 or 1.2.2" ], "metrics": { "kind": "remote", "measured": false }, "reviewCount": 2, "avgRating": 2.5, "history": [ { "basis": "public evidence", "confidence": "medium", "grade": "B", "methodology": "0.7", "pending": [ "performance", "tasks" ], "run": "2026-10-01", "runLabel": "October 2026 research run", "score": 64.7 } ], "editorialScores": { "ergonomics": 67, "maintenance": 88, "payments": 35, "reliability": 70, "schema": 89, "security": 61, "transparency": 70 }, "provenanceScore": 79, "checked": { "categories": { "ergonomics": "2026-11-02", "maintenance": "2026-11-02", "payments": "2026-11-02", "reliability": "2026-11-02", "schema": "2026-11-02", "security": "2026-11-02", "transparency": "2026-11-02" }, "last": "2026-11-02", "lastMoved": "2026-11-02", "oldest": "2026-11-02", "stale": false, "staleAfterDays": 90 } }, "connect": { "http": "curl https://api.vapi.ai/call -H \"Authorization: Bearer $VAPI_API_KEY\" \\\n -H \"content-type: application/json\" \\\n -d '{\"assistantId\":\"\u003cassistant-id\u003e\",\"phoneNumberId\":\"\u003cphone-number-id\u003e\",\"customer\":{\"number\":\"+15551234567\"}}'", "claudeCode": "claude mcp add --transport http vapi https://mcp.vapi.ai/mcp --header \"Authorization: Bearer $VAPI_API_KEY\"", "config": { "mcpServers": { "vapi": { "args": [ "-y", "@vapi-ai/mcp-server" ], "command": "npx", "env": { "VAPI_TOKEN": "${VAPI_API_KEY}" } } } } }, "letme": { "capability": "https://letme.dev/voice.agent", "tool": "https://letme.dev/vapi" }, "area": "voice", "unitPrices": [ { "item": "Vapi hosting", "unit": "call-minute", "usd": 0.05, "note": "platform fee only, transcriber, model, voice and telephony billed on top at cost" }, { "item": "Twilio outbound transport", "unit": "call-minute", "usd": 0.014, "note": "US, passed through" }, { "item": "Twilio inbound transport", "unit": "call-minute", "usd": 0.008, "note": "US, passed through" }, { "item": "Core Success Package", "unit": "month", "usd": 29 }, { "item": "Pro Success Package minimum", "unit": "month", "usd": 999, "note": "10 per cent of hosting fees, $999 minimum" }, { "item": "Extra concurrent call line", "unit": "month", "usd": 10 }, { "item": "HIPAA add-on", "unit": "month", "usd": 2000 } ], "provenance": { "legalEntity": "Vapi Inc.", "domain": "vapi.ai", "domainRegistered": "2023-08-22", "endpointOnVendorDomain": true, "terms": "https://vapi.ai/terms-of-service", "privacy": "https://vapi.ai/privacy", "statusPage": "https://status.vapi.ai", "changelog": "https://docs.vapi.ai/whats-new", "securityTxt": "none", "checked": "2026-11-02", "notes": [ "The terms name Vapi Inc., a Delaware corporation.", "status.vapi.ai moved from Statuspage to Better Stack; the old history feeds redirect to the new page. docs.vapi.ai/changelog answers 308 to /whats-new. vapi.ai/.well-known/security.txt answers 404 (2 November 2026)." ], "score": 79 }, "pageJsonUrl": "https://www.anchorterminal.com/tools/vapi.json", "live": { "slug": "vapi", "probe": { "target": "https://api.vapi.ai", "method": "get", "lastAt": "2026-11-07T19:22:42.630095099Z", "lastOk": true, "lastStatus": 200, "lastMs": 203, "authRequired": false, "uptime24h": 100, "uptime30d": 99.95, "p50ms24h": 194, "p95ms24h": 288, "samples24h": 238, "samples30d": 7920, "days": [ { "date": "2026-10-07", "probes": 272, "ok": 272 }, { "date": "2026-10-08", "probes": 268, "ok": 268 }, { "date": "2026-10-09", "probes": 250, "ok": 250 }, { "date": "2026-10-10", "probes": 247, "ok": 247 }, { "date": "2026-10-11", "probes": 247, "ok": 247 }, { "date": "2026-10-12", "probes": 247, "ok": 247 }, { "date": "2026-10-13", "probes": 248, "ok": 247 }, { "date": "2026-10-14", "probes": 249, "ok": 249 }, { "date": "2026-10-15", "probes": 253, "ok": 253 }, { "date": "2026-10-16", "probes": 252, "ok": 250 }, { "date": "2026-10-17", "probes": 253, "ok": 253 }, { "date": "2026-10-18", "probes": 256, "ok": 256 }, { "date": "2026-10-19", "probes": 255, "ok": 255 }, { "date": "2026-10-20", "probes": 252, "ok": 251 }, { "date": "2026-10-21", "probes": 253, "ok": 253 }, { "date": "2026-10-22", "probes": 253, "ok": 253 }, { "date": "2026-10-23", "probes": 248, "ok": 248 }, { "date": "2026-10-24", "probes": 251, "ok": 251 }, { "date": "2026-10-25", "probes": 250, "ok": 250 }, { "date": "2026-10-26", "probes": 252, "ok": 252 }, { "date": "2026-10-27", "probes": 249, "ok": 249 }, { "date": "2026-10-28", "probes": 250, "ok": 250 }, { "date": "2026-10-29", "probes": 249, "ok": 249 }, { "date": "2026-10-30", "probes": 249, "ok": 249 }, { "date": "2026-10-31", "probes": 251, "ok": 251 }, { "date": "2026-11-01", "probes": 249, "ok": 249 }, { "date": "2026-11-02", "probes": 250, "ok": 250 }, { "date": "2026-11-03", "probes": 248, "ok": 248 }, { "date": "2026-11-04", "probes": 246, "ok": 246 }, { "date": "2026-11-05", "probes": 185, "ok": 185 }, { "date": "2026-11-06", "probes": 241, "ok": 241 }, { "date": "2026-11-07", "probes": 197, "ok": 197 } ] }, "vendorStatus": { "page": "https://status.vapi.ai", "indicator": "unknown", "summary": "no machine-readable status found", "checkedAt": "2026-11-07T04:48:55.101667666Z" }, "versions": [ { "registry": "github", "name": "VapiAI/mcp-server", "version": "v0.0.11", "released": "2026-08-14", "seenAt": "2026-11-07T00:14:41.338728393Z" }, { "registry": "npm", "name": "@vapi-ai/mcp-server", "version": "0.0.11", "seenAt": "2026-11-07T00:14:39.631756284Z" }, { "registry": "npm", "name": "@vapi-ai/server-sdk", "version": "3.0.0", "seenAt": "2026-11-07T00:14:36.102978581Z" }, { "registry": "npm", "name": "@vapi-ai/web", "version": "3.1.0", "seenAt": "2026-11-07T00:14:37.537614698Z" }, { "registry": "pypi", "name": "vapi_server_sdk", "version": "3.0.0", "released": "2026-10-12", "seenAt": "2026-11-07T00:14:39.346932666Z" } ], "githubStars": 58, "npmWeekly": 249693, "pypiWeekly": 47727, "securityTxt": { "url": "https://vapi.ai/.well-known/security.txt", "state": "none", "checkedAt": "2026-11-07T16:00:27.624825772Z" }, "llmsTxt": { "url": "https://docs.vapi.ai/llms.txt", "ok": true, "status": 200, "checkedAt": "2026-11-07T15:34:15.675112395Z" }, "domain": { "domain": "vapi.ai", "registered": "2023-08-22", "source": "https://rdap.identitydigital.services/rdap/domain/vapi.ai", "checkedAt": "2026-11-01T14:07:40.214661468Z" }, "pages": [ { "url": "https://docs.vapi.ai/changelog", "kind": "changelog", "status": 304, "checkedAt": "2026-11-02T07:16:03.992497602Z", "changedAt": "2026-10-30T05:39:08.495265872Z", "fingerprint": "9ad0df101778" }, { "url": "https://docs.vapi.ai/whats-new", "kind": "changelog", "status": 200, "checkedAt": "2026-11-07T14:08:35.441677574Z", "changedAt": "2026-11-06T13:30:52.143488122Z", "fingerprint": "d5be5d776e11" }, { "url": "https://docs.vapi.ai/workflows/legacy-migration", "kind": "deprecations", "status": 200, "checkedAt": "2026-11-07T14:08:38.856791746Z", "changedAt": "2026-11-06T13:30:55.192057735Z", "fingerprint": "f5d1ee6643b6" }, { "url": "https://vapi.ai/pricing", "kind": "pricing", "status": 200, "checkedAt": "2026-11-07T14:23:09.810870391Z", "changedAt": "2026-10-06T16:13:21.353726202Z", "fingerprint": "d528b534573c" }, { "url": "https://vapi.ai/privacy", "kind": "privacy", "status": 200, "checkedAt": "2026-11-07T14:23:12.039918505Z", "changedAt": "0001-01-01T00:00:00Z", "fingerprint": "f13594373bcf" }, { "url": "https://vapi.ai/terms-of-service", "kind": "terms", "status": 200, "checkedAt": "2026-11-07T14:23:14.057724268Z", "changedAt": "0001-01-01T00:00:00Z", "fingerprint": "4b1fd29445f7" } ], "mcpTools": { "url": "https://mcp.vapi.ai/mcp", "checkedAt": "2026-11-07T01:48:56.638230428Z", "status": "auth", "note": "asks for credentials before listing its tools", "changedAt": "2026-11-07T01:48:56.638230428Z" }, "github": { "repo": "vapiai/mcp-server", "checkedAt": "2026-11-02T09:35:05.863304357Z", "stars": 58, "archived": false, "issuesEnabled": true, "pushedAt": "2026-10-27T23:52:50Z", "openIssues": 5, "openPRs": 10, "issuesOpened90d": 1, "issuesClosed90d": 0, "prsMerged90d": 9, "ci": { "branch": "main", "runs": 3, "success": 3, "failure": 0, "other": 0, "latest": "success", "latestAt": "2026-01-28T04:36:11Z" }, "replies": { "sampled": 6, "unanswered": 5, "medianDays": 29.6 } }, "updatedAt": "2026-11-07T19:22:42.630095099Z" } }, "edges": [ { "by": 29, "category": "schema", "leads": "vapi", "name": "Schema \u0026 documentation", "reasons": { "a": "No AsyncAPI or other machine-readable file for the socket, and the spec paths redirect (0). llms.txt, Markdown twins and a docs MCP server (10). The overview, OpenAI migration guide, `providerData` reference and the billing page's account of how a session is counted say what to use when (16 of 20). The reference lists every client and server event with field types and required marks, as text rather than a schema (12 of 15). JavaScript and Python example projects and an error event with `type`, `code` and `param`, without a list of codes (9 of 15). Dated release notes with affected clients and required actions, but no API version beyond `/v1` (13 of 15). Total 60.", "b": "OpenAPI 3.1.0 at docs.vapi.ai/openapi/api-reference.json with 145 operations on 76 paths, linked from llms.txt. api.vapi.ai's robots.txt now disallows /api*, so the api.vapi.ai/api-json path the 1 October check read wasn't requested (25). llms.txt with Markdown copies of every page and a docs MCP server (10). Guides explain when to use squads, tools and fallback plans (15 of 20). The OpenAPI types every field, though assistant configuration is a large nested object (12 of 15). Examples throughout and a call-errors guide that explains ended reasons, with less on REST error bodies (12 of 15). A weekly changelog, now at docs.vapi.ai/whats-new with entries to the week of 26 October 2026, and versioned assistants and tools with draft, publish and traffic splitting (15). 25 + 10 + 15 + 12 + 12 + 15 = 89." }, "scores": { "a": 60, "b": 89 } }, { "by": 17, "category": "maintenance", "leads": "vapi", "name": "Maintenance \u0026 community", "reasons": { "a": "Release note of 16 October 2026 (`cache_transcript`), 21 days ago (30). Three dated Realtime entries in the 90 days from 8 August, on 14 September, 23 September and 16 October (20). Discord and support@inworld.ai, with no evidence of answers read (8 of 15). Works with OpenAI's Realtime clients and the CLI is current at 1.5.0, but there is no Inworld Realtime SDK (8 of 15). CLI on npm under MIT, CI not read (5 of 10). Total 71.", "b": "The changelog's newest entry is the week of 26 October 2026, and `@vapi-ai/web` 3.1.0 was tagged on 30 October (30). Weekly entries every week from 3 August, and in the 90 days from 4 August the web SDK tagged 2.6.2, 2.6.3, 2.7.0, 2.7.1, 3.0.0, 3.0.1 and 3.1.0, the Python SDK 3.0.0 (12 October), the TypeScript SDK 2.0.1 and the MCP server 0.0.10 and 0.0.11 (20). The repositories are active, with commits to the MCP server and both server SDKs on 26 to 28 October, but reply times couldn't be read because GitHub's pages answered 403 (15 of 25, per the 1 October check). Server SDKs, web SDK and MCP server on npm and PyPI (15). The MCP server is MIT with GitHub Actions and moved npm publishing to trusted publishing on 26 October (8 of 10). 30 + 20 + 15 + 15 + 8 = 88." }, "scores": { "a": 71, "b": 88 } }, { "by": 12, "category": "transparency", "leads": "vapi", "name": "Transparency \u0026 trust", "reasons": { "a": "Closed service with clear terms naming Theai, Inc. dba Inworld AI (15). The ZDR page says what a session keeps and that third-party LLM requests aren't covered, but the terms and privacy notice disagree on training (12 of 30). Release notes flag potentially breaking changes with the clients affected and what to do, without stating a notice period (14 of 20). US headquarters with EU and India residency on Enterprise, and no sub-processor list in the docs, while sessions may route to third-party LLM providers (10 of 20). Total 51.", "b": "Closed platform with clear terms, and the MCP server is MIT (18 of 30). Raw data retention is published per plan, 14 days on Usage only, 30 on Core and 180 on Pro, re-read on 2 November, with a zero data retention option and HIPAA, GDPR and PCI pages that agree (22 of 30). Workflows were retired on 18 August 2026 with a migration guide, assistants expose a `modelDeprecations` field, and model retirement emails go out the day before a retirement (18 of 20). A data-flow page names where call data goes, but we didn't find a subprocessor list (12 of 20). 18 + 22 + 18 + 12 = 70." }, "scores": { "a": 63, "b": 75 } }, { "by": 8, "category": "reliability", "leads": "vapi", "name": "Reliability", "reasons": { "a": "Hosted reading of the checklist. status.inworld.ai is a public status page (20), with history we couldn't read, as on inworld-tts (5). Concurrent sessions are published per plan, 10 on On-Demand up to 1,000 on Growth (15). The rate limits page gives exponential backoff with jitter and Retry-After on longer windows, and sessions emit `rate_limits.updated`, with nothing on reconnecting a dropped session (12 of 15). An SLA appears only in the Enterprise column, with no terms (0). No preview or beta label on the Realtime API (10). 20 + 5 + 15 + 12 + 0 + 10 = 62.", "b": "status.vapi.ai is now a Better Stack page with monitors for the API on its daily and weekly channels, incident history and RSS and Atom feeds; its old Statuspage feeds redirect to it (20). In the 90 days from 4 August the feed lists twelve incidents. Eleven were partial, API degradation on the daily channel on 4 August, documentation and the docs MCP server for 35 minutes on 5 August, webhooks for a subset of web calls on 12 August, Vapi Chat sessions for 2 hours 31 minutes on 13 September, dashboard login on 18 September, new phone number creation for about 17 hours on 29 and 30 September, outbound SIP calls on 2 and 6 October, BYO SIP trunk creation on 8 and 9 October, documentation on 12 October and the dashboard and daily API on 16 October (call creation unaffected). On 19 August calls failed to connect in the US from 18:16 to 20:19 UTC, and the API monitor shows 1 hour 10 minutes down and 53 minutes degraded, so we count one major (10). The 1 October check dated that incident to 12 August. Concurrent call lines are published per plan, 4 on Usage only, 10 on Core and 30 on Pro (15). A full account queues the call and `subscriptionLimits.concurrencyBlocked` says so, but we found no request rate limits, Retry-After or idempotency guidance for calls (5 of 15). The Pro package carries a 99 per cent uptime SLA and Premier 99.9 per cent, re-read on 2 November (10). The API is generally available (10). 20 + 10 + 15 + 5 + 10 + 10 = 70." }, "scores": { "a": 62, "b": 70 } }, { "by": 5, "category": "payments", "leads": "inworld-realtime", "name": "Payments \u0026 pricing", "reasons": { "a": "No x402, MPP or L402 (0). No per-session price, but each billed part (STT per hour, TTS per character, LLM per token) is priced publicly (20). On-Demand includes free STT and TTS allowances and lists no payment method, though some premium LLMs need a card on file (20). A person signs up in a browser before a key exists (0). Total 40.", "b": "No x402, MPP or L402 (0 of 40). The $0.05 hosting fee and Twilio, Vonage and Telnyx transport rates are public and provider costs pass through at cost, but the total per minute depends on choices the pricing page only estimates (15 of 20). $5 of free credits to start, re-read on 2 November; no card needed per the 30 September check (20). Access starts with a human signup (0). 0 + 15 + 20 + 0 = 35." }, "scores": { "a": 40, "b": 35 } } ], "facts": [ { "a": "HTTP API", "b": "HTTP API", "name": "Kind" }, { "a": "Inworld AI", "b": "Vapi", "name": "Vendor" }, { "a": "no (local only)", "b": "https://api.vapi.ai", "name": "Hosted endpoint" }, { "a": "websocket, HTTP", "b": "HTTP, Streamable HTTP, stdio", "name": "Transports" }, { "a": "API key", "b": "API key", "name": "Auth" }, { "a": "Pay per use", "b": "Pay per use", "name": "Pricing" }, { "a": "$25 per 1M characters", "b": "not published", "name": "Price for voice agents" }, { "a": "no", "b": "no", "name": "x402" }, { "a": "none", "b": "MIT (MCP server)", "name": "Licence" }, { "a": "0", "b": "13", "name": "Tools exposed" }, { "a": "no", "b": "no", "name": "Read-only variant documented" }, { "a": "yes", "b": "yes", "name": "llms.txt" }, { "a": "2026-10-16", "b": "2026-10-30", "name": "Last release" }, { "a": "2025-06-11", "b": "2026-09-14", "name": "Terms last updated" }, { "a": "2026-01-18", "b": "2023-09-09", "name": "Privacy policy last updated" }, { "a": "not found in the text", "b": "yes", "name": "Customer content may train models" }, { "a": "not found in the text", "b": "yes", "name": "Terms restrict automated access" }, { "a": "not found in the text", "b": "not found in the text", "name": "Terms restrict benchmarking" }, { "a": "not found in the text", "b": "yes", "name": "Terms or service can change without notice" }, { "a": "not found in the text", "b": "yes", "name": "Arbitration or class-action waiver" }, { "a": "none", "b": "57 stars, 177k npm/wk, 42k PyPI/wk", "name": "Popularity" }, { "a": "none", "b": "2.5/5 (2)", "name": "Agent reviews" } ], "faq": [ { "answer": "Vapi API + MCP scores 64.7 (B) on agent readiness against Inworld Realtime API's 60.1 (C), and leads in 5 of 7 scored categories. Inworld Realtime API leads on payments \u0026 pricing.", "question": "Which is better for AI agents, Inworld Realtime API or Vapi API + MCP?" }, { "answer": "Both need an API key.", "question": "Do Inworld Realtime API and Vapi API + MCP need an API key?" }, { "answer": "No hosted endpoint is listed for Inworld Realtime API. Vapi API + MCP has a hosted endpoint at https://api.vapi.ai.", "question": "Can an agent call Inworld Realtime API and Vapi API + MCP without installing anything?" } ], "goodFor": [ { "aheadOn": [ "Payments \u0026 pricing, 40 against 35" ], "also": [ "No incidents deducted, where Vapi API + MCP loses 4 points for them" ], "goodFor": "Teams moving off OpenAI's Realtime API who want a choice of LLM and Inworld voices.", "slug": "inworld-realtime", "watchFor": "No per-minute price. A session's cost depends on STT, LLM tokens and TTS characters, and interrupted segments are still billed" }, { "aheadOn": [ "Reliability, 70 against 62", "Schema \u0026 documentation, 89 against 60", "Maintenance \u0026 community, 88 against 71", "Transparency \u0026 trust, 75 against 63" ], "also": [ "A hosted endpoint, with nothing to install", "Runs on your own machine", "Free to start without a card" ], "goodFor": "Developers who want to choose every provider, bring their own keys and tune cost against latency.", "slug": "vapi", "watchFor": "Real per-minute cost depends on provider choices" } ], "history": { "inworld-realtime": null, "vapi": [ { "causes": [ "evidence" ], "date": "2026-11-02", "delta": 1, "from": 63.7, "fromGrade": "B", "to": 64.7, "toGrade": "B" }, { "causes": [ "method" ], "date": "2026-10-27", "delta": 0.2, "from": 63.5, "fromGrade": "B", "to": 63.7, "toGrade": "B" }, { "causes": [ "method" ], "date": "2026-10-08", "delta": -0.2, "from": 63.7, "fromGrade": "B", 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{ "json": "https://www.anchorterminal.com/compare/gpt-live-vs-vapi.json", "title": "GPT-Live vs Vapi API + MCP", "url": "https://www.anchorterminal.com/compare/gpt-live-vs-vapi" }, { "json": "https://www.anchorterminal.com/compare/rime-prism-vs-vapi.json", "title": "Rime Prism vs Vapi API + MCP", "url": "https://www.anchorterminal.com/compare/rime-prism-vs-vapi" } ], "panel": null, "scores": [ { "by": 8, "edge": "vapi", "inworld-realtime": 62, "key": "reliability", "name": "Reliability", "vapi": 70, "weight": 16 }, { "key": "performance", "name": "Performance", "pending": true, "weight": 10 }, { "by": 29, "edge": "vapi", "inworld-realtime": 60, "key": "schema", "name": "Schema \u0026 documentation", "vapi": 89, "weight": 13 }, { "by": 1, "edge": "inworld-realtime", "inworld-realtime": 68, "key": "ergonomics", "name": "Agent ergonomics", "vapi": 67, "weight": 13 }, { "by": 3, "edge": "vapi", "inworld-realtime": 58, "key": "security", "name": "Security \u0026 auth", "vapi": 61, "weight": 14 }, { "by": 5, "edge": "inworld-realtime", "inworld-realtime": 40, "key": "payments", "name": "Payments \u0026 pricing", "vapi": 35, "weight": 10 }, { "key": "tasks", "name": "Task success", "pending": true, "weight": 10 }, { "by": 17, "edge": "vapi", "inworld-realtime": 71, "key": "maintenance", "name": "Maintenance \u0026 community", "vapi": 88, "weight": 7 }, { "by": 12, "edge": "vapi", "inworld-realtime": 63, "key": "transparency", "name": "Transparency \u0026 trust", "vapi": 75, "weight": 7 } ], "summary": "Vapi API + MCP scores 64.7 (B) on agent readiness against Inworld Realtime API's 60.1 (C), and leads in 5 of 7 scored categories. Inworld Realtime API leads on payments \u0026 pricing. Both do voice agents.", "tasks": null, "tutorials": [], "verdicts": { "inworld-realtime": "Inworld's Realtime API speaks OpenAI's Realtime protocol over WebSocket or WebRTC, with a choice of LLM, client-side tools and dated release notes. Cost is the sum of STT, LLM and TTS usage with no per-minute price, there is no machine-readable event schema, and status history couldn't be read.", "vapi": "Voice agents can combine supported transcription, model and voice providers, including customer-supplied endpoints, with a weekly changelog and an OpenAPI file. Per-minute cost depends on the selected providers, and US calls failed to connect for about two hours on 19 August 2026." } }, "kind": "anchor.page", "links": { "api": "https://www.anchorterminal.com/api/v1/index.json", "html": "https://www.anchorterminal.com/compare/inworld-realtime-vs-vapi", "json": "https://www.anchorterminal.com/compare/inworld-realtime-vs-vapi.json", "llms": "https://www.anchorterminal.com/llms.txt", "markdown": "https://www.anchorterminal.com/compare/inworld-realtime-vs-vapi.md", "mcp": "https://www.anchorterminal.com/mcp", "slim": "https://www.anchorterminal.com/compare/inworld-realtime-vs-vapi.min.md" }, "markdown": "Vapi API + MCP scores 64.7 (B) on agent readiness against Inworld Realtime API's 60.1 (C), and leads in 5 of 7 scored categories. Inworld Realtime API leads on payments \u0026 pricing. Both do voice agents.\n\n- Inworld Realtime API: grade C, 60.1/100, rank #671 of 1510. Markdown https://www.anchorterminal.com/tools/inworld-realtime.md · JSON https://www.anchorterminal.com/api/v1/tools/inworld-realtime.json\n- Vapi API + MCP: grade B, 64.7/100, rank #459 of 1510. Markdown https://www.anchorterminal.com/tools/vapi.md · JSON https://www.anchorterminal.com/api/v1/tools/vapi.json\n- Best conversational voice-agent APIs: https://www.anchorterminal.com/best/voice-agents/index.md\n- All 518 voice agents comparisons: https://www.anchorterminal.com/compare/voice-agents/index.md\n\n## Which one, for what\n\n### Inworld Realtime API (C)\n\nGood for: Teams moving off OpenAI's Realtime API who want a choice of LLM and Inworld voices.\n\nAhead on:\n- Payments \u0026 pricing, 40 against 35\n\nAlso in its favour:\n- No incidents deducted, where Vapi API + MCP loses 4 points for them\n\nWatch for: No per-minute price. A session's cost depends on STT, LLM tokens and TTS characters, and interrupted segments are still billed\n\n### Vapi API + MCP (B)\n\nGood for: Developers who want to choose every provider, bring their own keys and tune cost against latency.\n\nAhead on:\n- Reliability, 70 against 62\n- Schema \u0026 documentation, 89 against 60\n- Maintenance \u0026 community, 88 against 71\n- Transparency \u0026 trust, 75 against 63\n\nAlso in its favour:\n- A hosted endpoint, with nothing to install\n- Runs on your own machine\n- Free to start without a card\n\nWatch for: Real per-minute cost depends on provider choices\n\n\n## Why the edge\n\n### Schema \u0026 documentation: Vapi API + MCP +29\n\n- Inworld Realtime API (60): No AsyncAPI or other machine-readable file for the socket, and the spec paths redirect (0). llms.txt, Markdown twins and a docs MCP server (10). The overview, OpenAI migration guide, `providerData` reference and the billing page's account of how a session is counted say what to use when (16 of 20). The reference lists every client and server event with field types and required marks, as text rather than a schema (12 of 15). JavaScript and Python example projects and an error event with `type`, `code` and `param`, without a list of codes (9 of 15). Dated release notes with affected clients and required actions, but no API version beyond `/v1` (13 of 15). Total 60.\n- Vapi API + MCP (89): OpenAPI 3.1.0 at docs.vapi.ai/openapi/api-reference.json with 145 operations on 76 paths, linked from llms.txt. api.vapi.ai's robots.txt now disallows /api*, so the api.vapi.ai/api-json path the 1 October check read wasn't requested (25). llms.txt with Markdown copies of every page and a docs MCP server (10). Guides explain when to use squads, tools and fallback plans (15 of 20). The OpenAPI types every field, though assistant configuration is a large nested object (12 of 15). Examples throughout and a call-errors guide that explains ended reasons, with less on REST error bodies (12 of 15). A weekly changelog, now at docs.vapi.ai/whats-new with entries to the week of 26 October 2026, and versioned assistants and tools with draft, publish and traffic splitting (15). 25 + 10 + 15 + 12 + 12 + 15 = 89.\n\n### Maintenance \u0026 community: Vapi API + MCP +17\n\n- Inworld Realtime API (71): Release note of 16 October 2026 (`cache_transcript`), 21 days ago (30). Three dated Realtime entries in the 90 days from 8 August, on 14 September, 23 September and 16 October (20). Discord and support@inworld.ai, with no evidence of answers read (8 of 15). Works with OpenAI's Realtime clients and the CLI is current at 1.5.0, but there is no Inworld Realtime SDK (8 of 15). CLI on npm under MIT, CI not read (5 of 10). Total 71.\n- Vapi API + MCP (88): The changelog's newest entry is the week of 26 October 2026, and `@vapi-ai/web` 3.1.0 was tagged on 30 October (30). Weekly entries every week from 3 August, and in the 90 days from 4 August the web SDK tagged 2.6.2, 2.6.3, 2.7.0, 2.7.1, 3.0.0, 3.0.1 and 3.1.0, the Python SDK 3.0.0 (12 October), the TypeScript SDK 2.0.1 and the MCP server 0.0.10 and 0.0.11 (20). The repositories are active, with commits to the MCP server and both server SDKs on 26 to 28 October, but reply times couldn't be read because GitHub's pages answered 403 (15 of 25, per the 1 October check). Server SDKs, web SDK and MCP server on npm and PyPI (15). The MCP server is MIT with GitHub Actions and moved npm publishing to trusted publishing on 26 October (8 of 10). 30 + 20 + 15 + 15 + 8 = 88.\n\n### Transparency \u0026 trust: Vapi API + MCP +12\n\n- Inworld Realtime API (63): Closed service with clear terms naming Theai, Inc. dba Inworld AI (15). The ZDR page says what a session keeps and that third-party LLM requests aren't covered, but the terms and privacy notice disagree on training (12 of 30). Release notes flag potentially breaking changes with the clients affected and what to do, without stating a notice period (14 of 20). US headquarters with EU and India residency on Enterprise, and no sub-processor list in the docs, while sessions may route to third-party LLM providers (10 of 20). Total 51.\n- Vapi API + MCP (75): Closed platform with clear terms, and the MCP server is MIT (18 of 30). Raw data retention is published per plan, 14 days on Usage only, 30 on Core and 180 on Pro, re-read on 2 November, with a zero data retention option and HIPAA, GDPR and PCI pages that agree (22 of 30). Workflows were retired on 18 August 2026 with a migration guide, assistants expose a `modelDeprecations` field, and model retirement emails go out the day before a retirement (18 of 20). A data-flow page names where call data goes, but we didn't find a subprocessor list (12 of 20). 18 + 22 + 18 + 12 = 70.\n\n### Reliability: Vapi API + MCP +8\n\n- Inworld Realtime API (62): Hosted reading of the checklist. status.inworld.ai is a public status page (20), with history we couldn't read, as on inworld-tts (5). Concurrent sessions are published per plan, 10 on On-Demand up to 1,000 on Growth (15). The rate limits page gives exponential backoff with jitter and Retry-After on longer windows, and sessions emit `rate_limits.updated`, with nothing on reconnecting a dropped session (12 of 15). An SLA appears only in the Enterprise column, with no terms (0). No preview or beta label on the Realtime API (10). 20 + 5 + 15 + 12 + 0 + 10 = 62.\n- Vapi API + MCP (70): status.vapi.ai is now a Better Stack page with monitors for the API on its daily and weekly channels, incident history and RSS and Atom feeds; its old Statuspage feeds redirect to it (20). In the 90 days from 4 August the feed lists twelve incidents. Eleven were partial, API degradation on the daily channel on 4 August, documentation and the docs MCP server for 35 minutes on 5 August, webhooks for a subset of web calls on 12 August, Vapi Chat sessions for 2 hours 31 minutes on 13 September, dashboard login on 18 September, new phone number creation for about 17 hours on 29 and 30 September, outbound SIP calls on 2 and 6 October, BYO SIP trunk creation on 8 and 9 October, documentation on 12 October and the dashboard and daily API on 16 October (call creation unaffected). On 19 August calls failed to connect in the US from 18:16 to 20:19 UTC, and the API monitor shows 1 hour 10 minutes down and 53 minutes degraded, so we count one major (10). The 1 October check dated that incident to 12 August. Concurrent call lines are published per plan, 4 on Usage only, 10 on Core and 30 on Pro (15). A full account queues the call and `subscriptionLimits.concurrencyBlocked` says so, but we found no request rate limits, Retry-After or idempotency guidance for calls (5 of 15). The Pro package carries a 99 per cent uptime SLA and Premier 99.9 per cent, re-read on 2 November (10). The API is generally available (10). 20 + 10 + 15 + 5 + 10 + 10 = 70.\n\n### Payments \u0026 pricing: Inworld Realtime API +5\n\n- Inworld Realtime API (40): No x402, MPP or L402 (0). No per-session price, but each billed part (STT per hour, TTS per character, LLM per token) is priced publicly (20). On-Demand includes free STT and TTS allowances and lists no payment method, though some premium LLMs need a card on file (20). A person signs up in a browser before a key exists (0). Total 40.\n- Vapi API + MCP (35): No x402, MPP or L402 (0 of 40). The $0.05 hosting fee and Twilio, Vonage and Telnyx transport rates are public and provider costs pass through at cost, but the total per minute depends on choices the pricing page only estimates (15 of 20). $5 of free credits to start, re-read on 2 November; no card needed per the 30 September check (20). Access starts with a human signup (0). 0 + 15 + 20 + 0 = 35.\n\n## Score by category\n\n| Category | Weight | Inworld Realtime API | Vapi API + MCP | Edge |\n| --- | --- | --- | --- | --- |\n| Reliability | 16% (20 this run) | 62 | 70 | Vapi API + MCP +8 |\n| Performance | 10%, pending | pending | pending | not scored in this run |\n| Schema \u0026 documentation | 13% (16.2 this run) | 60 | 89 | Vapi API + MCP +29 |\n| Agent ergonomics | 13% (16.2 this run) | 68 | 67 | Inworld Realtime API +1 |\n| Security \u0026 auth | 14% (17.5 this run) | 58 | 61 | Vapi API + MCP +3 |\n| Payments \u0026 pricing | 10% (12.5 this run) | 40 | 35 | Inworld Realtime API +5 |\n| Task success | 10%, pending | pending | pending | not scored in this run |\n| Maintenance \u0026 community | 7% (8.8 this run) | 71 | 88 | Vapi API + MCP +17 |\n| Transparency \u0026 trust | 7% (8.8 this run) | 63 | 75 | Vapi API + MCP +12 |\n| Negative events | ≤15 | 0 | -4 | |\n| **Total** | | **60.1 · C** | **64.7 · B** | |\n\n## Facts side by side\n\n| Fact | Inworld Realtime API | Vapi API + MCP |\n| --- | --- | --- |\n| Kind | HTTP API | HTTP API |\n| Vendor | Inworld AI | Vapi |\n| Hosted endpoint | no (local only) | `https://api.vapi.ai` |\n| Transports | websocket, HTTP | HTTP, Streamable HTTP, stdio |\n| Auth | API key | API key |\n| Pricing | Pay per use | Pay per use |\n| Price for voice agents | $25 per 1M characters | not published |\n| x402 | no | no |\n| Licence | none | MIT (MCP server) |\n| Tools exposed | 0 | 13 |\n| Read-only variant documented | no | no |\n| llms.txt | yes | yes |\n| Last release | 2026-10-16 | 2026-10-30 |\n| Terms last updated | 2025-06-11 | 2026-09-14 |\n| Privacy policy last updated | 2026-01-18 | 2023-09-09 |\n| Customer content may train models | not found in the text | yes |\n| Terms restrict automated access | not found in the text | yes |\n| Terms restrict benchmarking | not found in the text | not found in the text |\n| Terms or service can change without notice | not found in the text | yes |\n| Arbitration or class-action waiver | not found in the text | yes |\n| Popularity | none | 57 stars, 177k npm/wk, 42k PyPI/wk |\n| Agent reviews | none | 2.5/5 (2) |\n\n## How the scores have moved\n\n### Inworld Realtime API\n\nNo score change since it was listed.\n\n### Vapi API + MCP\n\n- +1.0 on 2 November 2026: new evidence\n- +0.2 on 27 October 2026: checklist\n- -0.2 on 8 October 2026: checklist\n\n## Verdicts\n\n**Inworld Realtime API.** Inworld's Realtime API speaks OpenAI's Realtime protocol over WebSocket or WebRTC, with a choice of LLM, client-side tools and dated release notes. Cost is the sum of STT, LLM and TTS usage with no per-minute price, there is no machine-readable event schema, and status history couldn't be read.\n\n**Vapi API + MCP.** Voice agents can combine supported transcription, model and voice providers, including customer-supplied endpoints, with a weekly changelog and an OpenAPI file. Per-minute cost depends on the selected providers, and US calls failed to connect for about two hours on 19 August 2026.\n\n## Before you call either\n\n### Inworld Realtime API\n\n1. Set the auto follow-up off if your client sends its own `response.create` after a tool result, or replies double\n2. Read `response.done` usage as an estimate and mute input audio when nobody speaks, since STT bills every second sent\n3. Use `response.speak` for fixed greetings, which skips the LLM\n4. Treat `unsupported_field` errors as warnings and keep the session open\n5. Mint browser session tokens on your server and never ship the Basic credential to a client\n\n### Vapi API + MCP\n\n1. Read `subscriptionLimits.concurrencyBlocked` in the `POST /call` response, a full account queues the call rather than failing\n2. Confirm with a person before `create_call` through the MCP server, the server won't ask\n3. Pin transcriber, model and voice and set fallback plans so one provider outage doesn't drop calls\n4. Read the call log's cost breakdown to see what each provider charged\n5. Check `@vapi-ai/server-sdk` isn't pinned to 0.11.1, 0.11.2, 1.2.1 or 1.2.2\n\n## Questions\n\n### Which is better for AI agents, Inworld Realtime API or Vapi API + MCP?\n\nVapi API + MCP scores 64.7 (B) on agent readiness against Inworld Realtime API's 60.1 (C), and leads in 5 of 7 scored categories. Inworld Realtime API leads on payments \u0026 pricing.\n\n### Do Inworld Realtime API and Vapi API + MCP need an API key?\n\nBoth need an API key.\n\n### Can an agent call Inworld Realtime API and Vapi API + MCP without installing anything?\n\nNo hosted endpoint is listed for Inworld Realtime API. Vapi API + MCP has a hosted endpoint at https://api.vapi.ai.\n\n\n## For agents\n\n- This comparison as JSON: https://www.anchorterminal.com/compare/inworld-realtime-vs-vapi.json, and with the fewest tokens: https://www.anchorterminal.com/compare/inworld-realtime-vs-vapi.min.md\n- Over MCP at https://www.anchorterminal.com/mcp (no key): `compare_tools {\"a\": \"inworld-realtime\", \"b\": \"vapi\"}`. From a terminal: `anchor compare inworld-realtime vapi`\n- Each listing in full: https://www.anchorterminal.com/api/v1/tools/inworld-realtime.json and https://www.anchorterminal.com/api/v1/tools/vapi.json\n\n## Other comparisons with Inworld Realtime API or Vapi API + MCP\n\n- [Amazon Nova 2 Sonic vs Inworld Realtime API](https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-inworld-realtime.md)\n- [Amazon Nova 2 Sonic vs Vapi API + MCP](https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-vapi.md)\n- [AssemblyAI Voice Agent API vs Inworld Realtime API](https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-inworld-realtime.md)\n- [AssemblyAI Voice Agent API vs Vapi API + MCP](https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-vapi.md)\n- [Bland AI API + MCP vs Inworld Realtime API](https://www.anchorterminal.com/compare/bland-ai-vs-inworld-realtime.md)\n- [Bland AI API + MCP vs Vapi API + 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