{ "data": { "a": { "slug": "ultravox", "name": "Ultravox Realtime API", "vendor": "Ultravox (Fixie.ai)", "vendorUrl": "https://www.ultravox.ai", "kind": "http-api", "category": "voice-agents", "summary": "Hosted voice agents on Ultravox, an open-weight model that takes speech directly with no speech-to-text step and answers through a TTS voice.", "url": "https://www.anchorterminal.com/tools/ultravox", "markdownUrl": "https://www.anchorterminal.com/tools/ultravox.md", "slimMarkdownUrl": "https://www.anchorterminal.com/tools/ultravox.min.md", "jsonUrl": "https://www.anchorterminal.com/api/v1/tools/ultravox.json", "repo": "https://github.com/fixie-ai/ultravox", "license": "MIT (model code)", "transports": [ "http" ], "remoteUrl": "https://api.ultravox.ai/api", "packages": [ { "registry": "npm", "name": "ultravox-client" }, { "registry": "pypi", "name": "ultravox-client" } ], "auth": "api-key", "authNotes": "`X-API-Key` header on the REST API. Clients join a call with the `joinUrl` returned when it's created, so the key stays on your server.", "pricing": "usage", "pricingNotes": "Pay as you go at $0.05 a minute after 30 free minutes, capped at 5 concurrent calls. Pro is $100 a month (annual rate) at the same $0.05 a minute with no hard concurrency cap, the outbound scheduler, 5 custom voices and 20 RAG corpora. SIP costs 0.5 cents a minute (0.48 on Pro). Threads are $2 per 1M input tokens and $15 per 1M output. Enterprise is custom. Telephony from Twilio or other carriers is billed by them (https://www.ultravox.ai/pricing).", "priceSummary": "$100 / mo", "where": "hosted", "x402": { "level": "no", "evidence": "No x402 support in the docs, pricing page or MCP docs (checked 2026-09-30).", "endpoints": [] }, "toolCount": null, "popularity": { "githubStars": 4574, "npmWeekly": 17262, "pypiWeekly": null, "asOf": "2026-09-30" }, "docsUrl": "https://docs.ultravox.ai", "llmsTxt": "https://docs.ultravox.ai/llms.txt", "openapi": "https://api.ultravox.ai/api/schema/", "capabilities": [ "voice.agent", "voice.speech-to-speech", "voice.tools", "voice.telephony" ], "tags": [ "hosted", "open-weights", "no-card", "llms-txt", "openapi", "typescript", "python", "webhooks", "streaming", "speech-to-speech" ], "lastRelease": "2026-07-18", "graded": true, "anchor": { "graded": true, "score": 58.6, "grade": "C", "agentReady": false, "rank": 279, "ranked": true, "rankOf": 452, "categoryRank": 6, "methodology": "0.3", "run": "2026-10-01", "scores": { "ergonomics": 69, "maintenance": 43, "payments": 40, "reliability": 52, "schema": 84, "security": 46, "transparency": 75 }, "pending": [ "performance", "tasks" ], "assessment": { "confidence": "medium", "date": "2026-10-01" }, "negative": 0, "verdict": "Flat $0.05 a minute including model and built-in voices. No MCP server.", "strengths": [ "Flat $0.05 a minute including model and built-in voices", "Speech-native model with no separate STT stage, v0.7 weights public under MIT", "429 and 503 responses with Retry-After and backoff guidance", "Deprecation guide with a minimum 30-day window", "Privacy policy says voice data isn't used for training" ], "weaknesses": [ "No MCP server", "News page, deprecation guide and Python client last updated in December 2025", "Plain API keys with no scopes", "Pay as you go caps at 5 concurrent calls", "No subprocessor list or stated certification" ], "agentNotes": [ "Honour `Retry-After` on 429 and 503 when creating calls", "Pin the model string (`ultravox-v0.7` or `ultravox-v0.6`) rather than relying on the default", "Hand clients the `joinUrl`, never the API key", "Delete calls through the API when you need data removed, there's no retention setting", "Use call stages for multi-step flows instead of one long prompt" ], "metrics": { "kind": "remote", "measured": false }, "reviewCount": 2, "avgRating": 3, "history": [ { "basis": "public evidence", "confidence": "medium", "grade": "C", "methodology": "0.3", "pending": [ "performance", "tasks" ], "run": "2026-10-01", "runLabel": "October 2026 research run", "score": 58.6 } ], "editorialScores": { "ergonomics": 69, "maintenance": 43, "payments": 40, "reliability": 52, "schema": 84, "security": 46, "transparency": 67 }, "provenanceScore": 82 }, "connect": { "http": "curl -X POST https://api.ultravox.ai/api/calls -H \"X-API-Key: $ULTRAVOX_API_KEY\" \\\n -H \"content-type: application/json\" \\\n -d '{\"systemPrompt\":\"You are a friendly receptionist.\",\"voice\":\"Mark\"}'" }, "letme": { "capability": "https://letme.dev/voice.agent", "tool": "https://letme.dev/ultravox" }, "sameCompany": [ "ultravox-voice-cloning" ], "area": "voice", "unitPrices": [ { "item": "Ultravox Realtime", "unit": "call-minute", "usd": 0.05, "note": "model and built-in voices, telephony carrier costs extra" }, { "item": "SIP", "unit": "call-minute", "usd": 0.005, "note": "0.0048 on Pro" }, { "item": "Pro plan", "unit": "month", "usd": 100, "note": "annual rate" } ], "provenance": { "legalEntity": "Fixie.ai Inc.", "domain": "ultravox.ai", "domainRegistered": "2023-10-05", "endpointOnVendorDomain": true, "terms": "https://www.ultravox.ai/terms", "privacy": "https://www.ultravox.ai/privacy", "statusPage": "https://status.ultravox.ai", "changelog": "https://docs.ultravox.ai/changelog/news", "securityTxt": "none", "checked": "2026-09-30", "score": 82 }, "pageJsonUrl": "https://www.anchorterminal.com/tools/ultravox.json", "live": { "slug": "ultravox", "probe": { "target": "https://api.ultravox.ai/api", "method": "get", "lastAt": "2026-10-05T00:57:29.981356637Z", "lastOk": true, "lastStatus": 404, "lastMs": 110, "authRequired": false, "uptime24h": 100, "uptime30d": 100, "p50ms24h": 112, "p95ms24h": 155, "samples24h": 272, "samples30d": 1113, "days": [ { "date": "2026-09-30", "probes": 35, "ok": 35 }, { "date": "2026-10-01", "probes": 276, "ok": 276 }, { "date": "2026-10-02", "probes": 248, "ok": 248 }, { "date": "2026-10-03", "probes": 271, "ok": 271 }, { "date": "2026-10-04", "probes": 272, "ok": 272 }, { "date": "2026-10-05", "probes": 11, "ok": 11 } ] }, "vendorStatus": { "page": "https://status.ultravox.ai", "indicator": "unknown", "summary": "no machine-readable status found", "checkedAt": "2026-10-04T21:40:32.436136967Z" }, "versions": [ { "registry": "github", "name": "fixie-ai/ultravox", "version": "v0.6", "released": "2025-08-18", "seenAt": "2026-10-04T16:42:43.948571548Z" }, { "registry": "npm", "name": "ultravox-client", "version": "0.6.0", "seenAt": "2026-10-04T16:42:42.977160423Z" }, { "registry": "pypi", "name": "ultravox-client", "version": "0.1.0", "released": "2025-12-10", "seenAt": "2026-10-04T16:42:43.762434657Z" } ], "githubStars": 4573, "npmWeekly": 18685, "pypiWeekly": 117, "securityTxt": { "url": "https://ultravox.ai/.well-known/security.txt", "state": "none", "checkedAt": "2026-10-04T15:15:37.319054674Z" }, "llmsTxt": { "url": "https://docs.ultravox.ai/llms.txt", "ok": true, "status": 200, "checkedAt": "2026-10-04T15:18:20.699570722Z" }, "domain": { "domain": "ultravox.ai", "registered": "2023-10-05", "source": "https://rdap.identitydigital.services/rdap/domain/ultravox.ai", "checkedAt": "2026-10-04T13:04:52.103171331Z" }, "updatedAt": "2026-10-05T00:57:29.981356637Z" } }, "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", "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": 20, "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://api.vapi.ai/api-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": "2026-09-21", "graded": true, "anchor": { "graded": true, "score": 63.7, "grade": "B", "agentReady": false, "rank": 198, "ranked": true, "rankOf": 452, "categoryRank": 5, "methodology": "0.3", "run": "2026-10-01", "scores": { "ergonomics": 64, "maintenance": 88, "payments": 35, "reliability": 70, "schema": 89, "security": 58, "transparency": 76 }, "pending": [ "performance", "tasks" ], "assessment": { "confidence": "medium", "date": "2026-10-01" }, "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. Per-minute cost depends on the selected providers.", "strengths": [ "Any mix of transcriber, model and voice provider, or your own keys and endpoints", "OpenAPI file, 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 and publish since August 2026" ], "weaknesses": [ "Real per-minute cost depends on provider choices", "Usage only has 4 concurrent lines and 14 days of retention", "MCP tools that place calls or buy numbers carry no annotations", "No request rate limits or Retry-After guidance 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 `vapi_create_call` or `vapi_buy_phone_number`, 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": "0.3", "pending": [ "performance", "tasks" ], "run": "2026-10-01", "runLabel": "October 2026 research run", "score": 63.7 } ], "editorialScores": { "ergonomics": 64, "maintenance": 88, "payments": 35, "reliability": 70, "schema": 89, "security": 58, "transparency": 70 }, "provenanceScore": 82 }, "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/changelog", "securityTxt": "none", "checked": "2026-10-01", "notes": [ "The terms name Vapi Inc., a Delaware corporation." ], "score": 82 }, "pageJsonUrl": "https://www.anchorterminal.com/tools/vapi.json", "live": { "slug": "vapi", "probe": { "target": "https://api.vapi.ai", "method": "get", "lastAt": "2026-10-05T00:57:30.092583865Z", "lastOk": true, "lastStatus": 200, "lastMs": 207, "authRequired": false, "uptime24h": 100, "uptime30d": 100, "p50ms24h": 190, "p95ms24h": 551, "samples24h": 272, "samples30d": 1113, "days": [ { "date": "2026-09-30", "probes": 35, "ok": 35 }, { "date": "2026-10-01", "probes": 276, "ok": 276 }, { "date": "2026-10-02", "probes": 248, "ok": 248 }, { "date": "2026-10-03", "probes": 271, "ok": 271 }, { "date": "2026-10-04", "probes": 272, "ok": 272 }, { "date": "2026-10-05", "probes": 11, "ok": 11 } ] }, "vendorStatus": { "page": "https://status.vapi.ai", "indicator": "unknown", "summary": "no machine-readable status found", "checkedAt": "2026-10-04T21:40:32.91562276Z" }, "versions": [ { "registry": "github", "name": "VapiAI/mcp-server", "version": "v0.0.11", "released": "2026-08-14", "seenAt": "2026-10-04T16:43:12.477208468Z" }, { "registry": "npm", "name": "@vapi-ai/mcp-server", "version": "0.0.11", "seenAt": "2026-10-04T16:43:10.657227109Z" }, { "registry": "npm", "name": "@vapi-ai/server-sdk", "version": "2.0.1", "seenAt": "2026-10-04T16:43:06.847289486Z" }, { "registry": "npm", "name": "@vapi-ai/web", "version": "2.7.1", "seenAt": "2026-10-04T16:43:09.259416721Z" }, { "registry": "pypi", "name": "vapi_server_sdk", "version": "1.11.1", "released": "2026-05-20", "seenAt": "2026-10-04T16:43:10.468923211Z" } ], "githubStars": 57, "npmWeekly": 205182, "pypiWeekly": 39699, "securityTxt": { "url": "https://vapi.ai/.well-known/security.txt", "state": "none", "checkedAt": "2026-10-04T15:15:46.43020372Z" }, "llmsTxt": { "url": "https://docs.vapi.ai/llms.txt", "ok": true, "status": 200, "checkedAt": "2026-10-04T15:18:23.657652287Z" }, "domain": { "domain": "vapi.ai", "registered": "2023-08-22", "source": "https://rdap.identitydigital.services/rdap/domain/vapi.ai", "checkedAt": "2026-10-04T13:10:12.103273987Z" }, "pages": [ { "url": "https://docs.vapi.ai/changelog", "kind": "changelog", "status": 200, "checkedAt": "2026-10-04T15:44:13.606342765Z", "changedAt": "2026-10-03T15:32:20.588337898Z", "fingerprint": "ec991822798a" }, { "url": "https://docs.vapi.ai/whats-new", "kind": "changelog", "status": 200, "checkedAt": "2026-10-01T13:13:04.652536748Z", "changedAt": "0001-01-01T00:00:00Z", "fingerprint": "8b20b96ab7a4" }, { "url": "https://docs.vapi.ai/workflows/legacy-migration", "kind": "deprecations", "status": 200, "checkedAt": "2026-10-04T15:44:25.802628589Z", "changedAt": "0001-01-01T00:00:00Z", "fingerprint": "9f62a32477a4" }, { "url": "https://vapi.ai/pricing", "kind": "pricing", "status": 200, "checkedAt": "2026-10-04T15:48:41.681772611Z", "changedAt": "0001-01-01T00:00:00Z", "fingerprint": "f3c0afec077f" }, { "url": "https://vapi.ai/privacy", "kind": "privacy", "status": 304, "checkedAt": "2026-10-04T15:48:43.888276245Z", "changedAt": "0001-01-01T00:00:00Z", "fingerprint": "f13594373bcf" }, { "url": "https://vapi.ai/terms-of-service", "kind": "terms", "status": 304, "checkedAt": "2026-10-04T15:48:45.895499196Z", "changedAt": "0001-01-01T00:00:00Z", "fingerprint": "4b1fd29445f7" } ], "updatedAt": "2026-10-05T00:57:30.092583865Z" } }, "summary": "Vapi API + MCP has a score of 63.7 (B) against Ultravox Realtime API's 58.6 (C). Both do voice agent. The largest gap is maintenance \u0026 community, 45 points." }, "kind": "anchor.page", "links": { "api": "https://www.anchorterminal.com/api/v1/index.json", "html": "https://www.anchorterminal.com/compare/ultravox-vs-vapi", "json": "https://www.anchorterminal.com/compare/ultravox-vs-vapi.json", "llms": "https://www.anchorterminal.com/llms.txt", "markdown": "https://www.anchorterminal.com/compare/ultravox-vs-vapi.md", "slim": "https://www.anchorterminal.com/compare/ultravox-vs-vapi.min.md" }, "markdown": "Vapi API + MCP has a score of 63.7 (B) against Ultravox Realtime API's 58.6 (C). Both do voice agent. The largest gap is maintenance \u0026 community, 45 points.\n\n- Ultravox Realtime API: grade C, 58.6/100, rank #279 of 452. Markdown https://www.anchorterminal.com/tools/ultravox.md · JSON https://www.anchorterminal.com/api/v1/tools/ultravox.json\n- Vapi API + MCP: grade B, 63.7/100, rank #198 of 452. Markdown https://www.anchorterminal.com/tools/vapi.md · JSON https://www.anchorterminal.com/api/v1/tools/vapi.json\n\n## Which one, for what\n\nPick Ultravox Realtime API for agent ergonomics (+5), payments \u0026 pricing (+5).\n\nPick Vapi API + MCP for reliability (+18), schema \u0026 documentation (+5), security \u0026 auth (+12), maintenance \u0026 community (+45).\n\n## Score by category\n\n| Category | Weight | Ultravox Realtime API | Vapi API + MCP | Edge |\n| --- | --- | --- | --- | --- |\n| Reliability | 16% (20 this run) | 52 | 70 | Vapi API + MCP +18 |\n| Performance | 10%, pending | pending | pending | not scored in this run |\n| Schema \u0026 documentation | 13% (16.2 this run) | 84 | 89 | Vapi API + MCP +5 |\n| Agent ergonomics | 13% (16.2 this run) | 69 | 64 | Ultravox Realtime API +5 |\n| Security \u0026 auth | 14% (17.5 this run) | 46 | 58 | Vapi API + MCP +12 |\n| Payments \u0026 pricing | 10% (12.5 this run) | 40 | 35 | Ultravox Realtime API +5 |\n| Task success | 10%, pending | pending | pending | not scored in this run |\n| Maintenance \u0026 community | 7% (8.8 this run) | 43 | 88 | Vapi API + MCP +45 |\n| Transparency \u0026 trust | 7% (8.8 this run) | 75 | 76 | Vapi API + MCP +1 |\n| Negative events | ≤15 | 0 | -4 | |\n| **Total** | | **58.6 · C** | **63.7 · B** | |\n\n## Facts side by side\n\n| Fact | Ultravox Realtime API | Vapi API + MCP |\n| --- | --- | --- |\n| Kind | HTTP API | HTTP API |\n| Vendor | Ultravox (Fixie.ai) | Vapi |\n| Hosted endpoint | `https://api.ultravox.ai/api` | `https://api.vapi.ai` |\n| Transports | HTTP | HTTP, Streamable HTTP, stdio |\n| Auth | API key | API key |\n| Pricing | Pay per use | Pay per use |\n| x402 | no | no |\n| Licence | MIT (model code) | MIT (MCP server) |\n| Tools exposed | none | 20 |\n| Context cost (tools/list) | n/a | n/a |\n| p95 latency | not measured yet | not measured yet |\n| Availability (30d) | not measured yet | not measured yet |\n| Read-only variant documented | no | no |\n| llms.txt | yes | yes |\n| MCP registry | not listed | not listed |\n| Last release | 2026-07-18 | 2026-09-21 |\n| Popularity | 4.6k stars, 17k npm/wk | 57 stars, 177k npm/wk, 42k PyPI/wk |\n| Agent reviews | 3/5 (2) | 2.5/5 (2) |\n\n## Verdicts\n\n**Ultravox Realtime API.** Flat $0.05 a minute including model and built-in voices. No MCP server.\n\n**Vapi API + MCP.** Voice agents can combine supported transcription, model and voice providers, including customer-supplied endpoints. Per-minute cost depends on the selected providers.\n\n## Before you call either\n\n### Ultravox Realtime API\n\n1. Honour `Retry-After` on 429 and 503 when creating calls\n2. Pin the model string (`ultravox-v0.7` or `ultravox-v0.6`) rather than relying on the default\n3. Hand clients the `joinUrl`, never the API key\n4. Delete calls through the API when you need data removed, there's no retention setting\n5. Use call stages for multi-step flows instead of one long prompt\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 `vapi_create_call` or `vapi_buy_phone_number`, 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## Other comparisons with Ultravox Realtime API or Vapi API + MCP\n\n- [Bland AI API + MCP vs Ultravox Realtime API](https://www.anchorterminal.com/compare/bland-ai-vs-ultravox.md)\n- [Bland AI API + MCP vs Vapi API + MCP](https://www.anchorterminal.com/compare/bland-ai-vs-vapi.md)\n- [Bolna API + MCP vs Ultravox Realtime API](https://www.anchorterminal.com/compare/bolna-vs-ultravox.md)\n- [Bolna API + MCP vs Vapi API + MCP](https://www.anchorterminal.com/compare/bolna-vs-vapi.md)\n- [Deepgram Voice Agent API vs Ultravox Realtime API](https://www.anchorterminal.com/compare/deepgram-voice-agent-vs-ultravox.md)\n- [Deepgram Voice Agent API vs Vapi API + MCP](https://www.anchorterminal.com/compare/deepgram-voice-agent-vs-vapi.md)\n- [ElevenLabs Agents API + MCP vs Ultravox Realtime API](https://www.anchorterminal.com/compare/elevenlabs-agents-vs-ultravox.md)\n- [ElevenLabs Agents API + MCP vs Vapi API + MCP](https://www.anchorterminal.com/compare/elevenlabs-agents-vs-vapi.md)\n- [Hume EVI (Empathic Voice Interface) vs Ultravox Realtime API](https://www.anchorterminal.com/compare/hume-evi-vs-ultravox.md)\n- [Hume EVI (Empathic Voice Interface) vs Vapi API + MCP](https://www.anchorterminal.com/compare/hume-evi-vs-vapi.md)\n- [Retell AI API + MCP vs Ultravox Realtime API](https://www.anchorterminal.com/compare/retell-ai-vs-ultravox.md)\n- [Retell AI API + MCP vs Vapi API + MCP](https://www.anchorterminal.com/compare/retell-ai-vs-vapi.md)\n- [Synthflow API + MCP vs Ultravox Realtime API](https://www.anchorterminal.com/compare/synthflow-vs-ultravox.md)\n- [Synthflow API + MCP vs Vapi API + MCP](https://www.anchorterminal.com/compare/synthflow-vs-vapi.md)\n- [Ultravox Realtime API vs Vogent API](https://www.anchorterminal.com/compare/ultravox-vs-vogent.md)\n- [Vapi API + MCP vs Vogent API](https://www.anchorterminal.com/compare/vapi-vs-vogent.md)\n", "meta": { "attribution": "Anchor Terminal (https://www.anchorterminal.com)", "docs": "https://www.anchorterminal.com/docs/", "generatedAt": "2026-10-05", "license": "CC-BY-4.0", "method": "https://www.anchorterminal.com/benchmark/", "methodology": "0.3", "openapi": "https://www.anchorterminal.com/openapi.json", "preview": false, "run": "2026-10-01", "runLabel": "October 2026 research run" }, "page": { "breadcrumbs": [ { "name": "Home", "url": "https://www.anchorterminal.com/" }, { "name": "Compare", "url": "https://www.anchorterminal.com/compare/" }, { "name": "Ultravox Realtime API vs Vapi API + MCP", "url": "" } ], "description": "Vapi API + MCP has a score of 63.7 (B) against Ultravox Realtime API's 58.6 (C). Both do voice agent. The largest gap is maintenance \u0026 community, 45 points. Category scores, facts, verdicts and agent notes side by side.", "facts": [ "Ultravox Realtime API C 58.6", "Vapi API + MCP B 63.7", "scores" ], "h1": "Ultravox Realtime API vs Vapi API + MCP", "image": "https://www.anchorterminal.com/assets/og/compare-ultravox-vs-vapi.png", "path": "/compare/ultravox-vs-vapi", "published": "2026-10-01", "section": "tools", "title": "Ultravox Realtime API vs Vapi API + MCP for AI agents", "toc": null, "updated": "2026-10-05", "url": "https://www.anchorterminal.com/compare/ultravox-vs-vapi" }, "tokens": { "markdown": 1600, "slim": 330 }, "version": 1 }