{ "data": { "a": { "slug": "openai-realtime", "name": "OpenAI Realtime API", "vendor": "OpenAI", "vendorUrl": "https://openai.com", "kind": "http-api", "category": "voice-agents", "summary": "OpenAI's Realtime API runs spoken conversations with speech-to-speech models such as `gpt-realtime-2.1`. Clients connect over WebRTC, WebSocket or SIP, and sessions support interruptions, function calling and remote MCP tools.", "url": "https://www.anchorterminal.com/tools/openai-realtime", "markdownUrl": "https://www.anchorterminal.com/tools/openai-realtime.md", "slimMarkdownUrl": "https://www.anchorterminal.com/tools/openai-realtime.min.md", "jsonUrl": "https://www.anchorterminal.com/api/v1/tools/openai-realtime.json", "repo": "https://github.com/openai/openai-agents-js", "license": "Proprietary service. The service terms on openai.com were not read. The Agents SDK for TypeScript and the OpenAPI description are MIT", "transports": [ "http" ], "remoteUrl": "https://api.openai.com/v1/realtime", "packages": [ { "registry": "npm", "name": "@openai/agents" }, { "registry": "npm", "name": "@openai/agents-realtime" } ], "auth": "api-key", "authNotes": "Self-serve API key from platform.openai.com, sent as a Bearer header on server WebSocket connections and call-control requests. For browsers and phones, a server calls `POST /v1/realtime/client_secrets` for a client secret (`ek_`) that lasts 10 seconds to 2 hours, 10 minutes by default, and can start several sessions until it expires. The browser WebSocket example passes the secret as a subprotocol. SIP calls are tied to a project by the project ID in the SIP address.", "pricing": "usage", "pricingNotes": "Per 1M tokens on `gpt-realtime-2.1`. Audio $32.00 in, $0.40 cached and $64.00 out, text $4.00 in and $24.00 out, image $5.00 in. `gpt-realtime-2.1-mini` is $10.00 and $20.00 for audio. Each response re-sends the whole conversation, and input transcription is billed separately. Usage tiers start at $5 of credit purchases. Whether the Free tier covers Realtime models was not established (https://developers.openai.com/api/docs/pricing.md, checked 2026-10-09).", "priceSummary": "Pay per use", "where": "hosted", "x402": { "level": "no", "evidence": "No x402, MPP or L402 in the Realtime guides, the pricing page or the OpenAPI file (checked 2026-10-09).", "endpoints": [] }, "toolCount": null, "popularity": { "githubStars": null, "npmWeekly": null, "pypiWeekly": null, "asOf": "2026-10-09" }, "docsUrl": "https://developers.openai.com/api/docs/guides/realtime", "llmsTxt": "https://developers.openai.com/api/docs/llms.txt", "openapi": "https://github.com/openai/openai-openapi/blob/main/openapi.yaml", "capabilities": [ "voice.agent", "voice.speech-to-speech", "voice.tools", "voice.telephony" ], "tags": [ "hosted", "usage-priced", "closed-source", "speech-to-speech", "webrtc", "websocket", "sip", "streaming", "typescript", "python", "openapi", "llms-txt", "api-key", "function-calling", "mcp-client", "status-page" ], "lastRelease": "2026-07-28", "graded": true, "anchor": { "graded": true, "score": 63.3, "grade": "B", "agentReady": false, "rank": 400, "ranked": true, "rankOf": 950, "categoryRank": 7, "methodology": "0.4", "run": "2026-10-01", "scores": { "ergonomics": 76, "maintenance": 52, "payments": 20, "reliability": 67, "schema": 84, "security": 61, "transparency": 71 }, "pending": [ "performance", "tasks" ], "assessment": { "confidence": "low", "date": "2026-10-09" }, "negative": 0, "verdict": "A generally available speech-to-speech API with WebRTC, WebSocket and SIP transports, a public OpenAPI file that types its events, and per-token prices. Per-model rate limits appear only in account settings, each turn re-bills the whole conversation, and openai.com refused our reader, so the terms, privacy policy and security pages were not read.", "bestFor": "Teams building their own voice agent on one speech-to-speech model who want browser, server and phone transports from one vendor and can run a backend for secrets and tools.", "strengths": [ "The OpenAPI 3.1 file in `openai/openai-openapi` covers nine Realtime paths and types 13 client events and 48 server events as schemas.", "Browser clients use client secrets that expire after 10 seconds to 2 hours, 10 minutes by default, so the API key stays on a server.", "Remote MCP tools accept an `allowed_tools` list, and `require_approval` defaults to `always` in the OpenAPI file.", "SIP calls connect at `sip.api.openai.com` with accept, reject, refer and hangup endpoints and a signed incoming-call webhook.", "The data controls page lists `/v1/realtime` with no training use, 30-day abuse logs, no stored application state and Zero Data Retention eligibility." ], "weaknesses": [ "openai.com answered 403 to our reader, so the service terms, privacy policy, sub-processor list and security pages were not read.", "Realtime rate limits are shown only in account settings. The public table gives numbers for GPT-6 model families only.", "Every response re-sends the whole conversation, so later turns cost more. Audio is $32 in and $64 out per 1M tokens on `gpt-realtime-2.1`.", "The status feed names Realtime among affected components in five incidents between 24 July and 6 October 2026, with durations not shown in the feed.", "Session settings attached to a client secret can be overridden by the client connection, per the client secret reference." ], "agentNotes": [ "Create a client secret on a server with `POST /v1/realtime/client_secrets` and give browsers only the `ek_` value. Never ship the API key.", "After a response with MCP calls finishes, send another `response.create`. The API does not create the follow-up response itself.", "Set `truncation` with a `retention_ratio` below 1 and `token_limits.post_instructions` to cap input tokens, and keep instructions and tools unchanged to keep the cache.", "On a WebSocket, stop playback on `input_audio_buffer.speech_started` and send `conversation.item.truncate` with `audio_end_ms`. WebRTC and SIP truncate on the server.", "Use `gpt-realtime-2.1` or `gpt-realtime-2.1-mini`. `gpt-realtime` and `gpt-realtime-mini` shut down on 20 January 2027." ], "metrics": { "kind": "remote", "measured": false }, "reviewCount": 0, "avgRating": 0, "history": [ { "basis": "public evidence", "confidence": "low", "grade": "B", "methodology": "0.4", "pending": [ "performance", "tasks" ], "run": "2026-10-01", "runLabel": "October 2026 research run", "score": 63.3 } ], "editorialScores": { "ergonomics": 76, "maintenance": 52, "payments": 20, "reliability": 67, "schema": 84, "security": 61, "transparency": 58 }, "provenanceScore": 84 }, "connect": { "install": "npm install @openai/agents", "http": "curl -X POST https://api.openai.com/v1/realtime/client_secrets \\\n -H \"Authorization: Bearer $OPENAI_API_KEY\" -H \"Content-Type: application/json\" \\\n -d '{\"session\": {\"type\": \"realtime\", \"model\": \"gpt-realtime-2.1\"}}'" }, "letme": { "capability": "https://letme.dev/voice.agent", "tool": "https://letme.dev/openai-realtime" }, "sameCompany": [ "openai-api", "openai-embeddings", "openai-guardrails", "openai-moderation", "openai-image-api", "openai-sora", "openai-speech-to-text", "openai-agents-sdk", "openai-decisions-api", "openai-codex" ], "area": "voice", "unitPrices": [ { "item": "gpt-realtime-2.1 audio input", "unit": "1m-tokens", "usd": 32, "note": "$0.40 cached. 1 token per 100 ms of user audio, about $0.019 a minute before caching" }, { "item": "gpt-realtime-2.1 audio output", "unit": "1m-tokens", "usd": 64, "note": "1 token per 50 ms of assistant audio, about $0.077 a minute" }, { "item": "gpt-realtime-2.1 text input", "unit": "1m-tokens", "usd": 4, "note": "$0.40 cached" }, { "item": "gpt-realtime-2.1 text output", "unit": "1m-tokens", "usd": 24 }, { "item": "gpt-realtime-2.1-mini audio input", "unit": "1m-tokens", "usd": 10, "note": "$0.30 cached" }, { "item": "gpt-realtime-2.1-mini audio output", "unit": "1m-tokens", "usd": 20 } ], "provenance": { "legalEntity": "OpenAI", "domain": "openai.com", "domainRegistered": "2007-01-19", "endpointOnVendorDomain": true, "terms": "https://openai.com/policies/services-agreement/", "privacy": "https://openai.com/policies/privacy-policy/", "statusPage": "https://status.openai.com", "changelog": "https://developers.openai.com/api/docs/changelog", "securityTxt": "unknown", "checked": "2026-10-09", "notes": [ "The API, WebRTC and SIP endpoints are on api.openai.com and sip.api.openai.com. The docs are on developers.openai.com.", "RDAP for openai.com gives a registration date of 2007-01-19.", "The legal entity was not read. The SDK licence file says Copyright (c) 2025 OpenAI.", "robots.txt answered 200 on developers.openai.com and openai.com, allowing the pages read, and 404 on status.openai.com, which means no rules.", "openai.com answered our researcher with a bot check on 9 October 2026, so the terms and privacy policy were not read on that day. The links are the two documents OpenAI's other listings here carry. openai.com answers our policy reader with HTTP 403 as well, so neither document has been read and both are recorded as unreadable." ], "score": 84 }, "pageJsonUrl": "https://www.anchorterminal.com/tools/openai-realtime.json", "live": { "slug": "openai-realtime", "probe": { "target": "https://api.openai.com/v1/realtime", "method": "get", "lastAt": "2026-10-10T02:55:04.55025386Z", "lastOk": true, "lastStatus": 405, "lastMs": 133, "authRequired": false, "uptime24h": 100, "uptime30d": 100, "p50ms24h": 153, "p95ms24h": 204, "samples24h": 115, "samples30d": 115, "days": [ { "date": "2026-10-09", "probes": 85, "ok": 85 }, { "date": "2026-10-10", "probes": 30, "ok": 30 } ] }, "vendorStatus": { "page": "https://status.openai.com", "indicator": "minor", "summary": "Partial System Degradation", "checkedAt": "2026-10-10T02:50:36.234904992Z" }, "versions": [ { "registry": "github", "name": "openai/openai-agents-js", "version": "@openai/agents-extensions@0.20.0", "released": "2026-10-08", "seenAt": "2026-10-09T17:10:29.452928495Z" }, { "registry": "npm", "name": "@openai/agents", "version": "0.20.0", "seenAt": "2026-10-09T17:10:27.202909251Z" }, { "registry": "npm", "name": "@openai/agents-realtime", "version": "0.20.0", "seenAt": "2026-10-09T17:10:27.531105633Z" } ], "githubStars": 3903, "npmWeekly": 2125326, "pages": [ { "url": "https://developers.openai.com/api/docs/pricing.md", "kind": "pricing", "status": 200, "checkedAt": "2026-10-09T18:36:10.419663305Z", "changedAt": "0001-01-01T00:00:00Z", "fingerprint": "742c4d3c6b71" } ], "updatedAt": "2026-10-10T02:55:04.55025386Z" } }, "answer": "Retell AI API + MCP scores 69.1 (B) on agent readiness against OpenAI Realtime API's 63.3 (B), and leads in 5 of 7 scored categories. OpenAI Realtime API leads on reliability and agent ergonomics.", "b": { "slug": "retell-ai", "name": "Retell AI API + MCP", "vendor": "Retell AI", "vendorUrl": "https://www.retellai.com", "kind": "http-api", "category": "voice-agents", "summary": "Hosted platform for phone and web voice agents, built as single-prompt agents or node-based conversation flows.", "url": "https://www.anchorterminal.com/tools/retell-ai", "markdownUrl": "https://www.anchorterminal.com/tools/retell-ai.md", "slimMarkdownUrl": "https://www.anchorterminal.com/tools/retell-ai.min.md", "jsonUrl": "https://www.anchorterminal.com/api/v1/tools/retell-ai.json", "repo": "https://github.com/RetellAI/retell-typescript-sdk", "license": "Apache-2.0 (SDKs)", "transports": [ "http", "streamable-http" ], "remoteUrl": "https://api.retellai.com", "packages": [ { "registry": "npm", "name": "retell-sdk" }, { "registry": "npm", "name": "retell-client-js-sdk" }, { "registry": "pypi", "name": "retell-sdk" } ], "auth": "api-key", "authNotes": "Bearer API key for the REST API and the hosted MCP server at `https://mcp.retellai.com`. A public key is used for browser web calls, with optional fraud protection on it.", "pricing": "usage", "pricingNotes": "Pay as you go with $10 of free credits, priced per component. Voice infrastructure $0.055 a minute, Retell and most third-party voices $0.015 (ElevenLabs $0.04), telephony $0.015 on Retell numbers, and the LLM from $0.0016 to $0.32 a minute depending on model. The vendor puts the total at $0.07 to $0.31 a minute. Speech-to-speech models run $0.07 (GPT Realtime mini) to $0.38 a minute. Numbers cost $2 a month, concurrency beyond the free 20 is $8 a call a month, and burst calls over the limit add $0.10 a minute. Enterprise pricing is custom (https://www.retellai.com/pricing).", "priceSummary": "$2 / 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": 62, "npmWeekly": 242906, "pypiWeekly": null, "asOf": "2026-09-30" }, "docsUrl": "https://docs.retellai.com", "llmsTxt": "https://docs.retellai.com/llms.txt", "openapi": "https://docs.retellai.com/openapi-final.yaml", "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": "2026-09-14", "graded": true, "anchor": { "graded": true, "score": 69.1, "grade": "B", "agentReady": false, "rank": 196, "ranked": true, "rankOf": 950, "categoryRank": 2, "methodology": "0.4", "run": "2026-10-01", "scores": { "ergonomics": 60, "maintenance": 85, "payments": 40, "reliability": 60, "schema": 92, "security": 76, "transparency": 76 }, "pending": [ "performance", "tasks" ], "assessment": { "confidence": "medium", "date": "2026-10-01" }, "negative": 0, "verdict": "Published per-minute price for every component, from $0.07 a minute all in. Call data kept indefinitely unless retention is set per agent.", "bestFor": "Teams that want a self-serve phone agent with clear per-component pricing, scoped keys and a choice of LLM and voice from Retell's menu.", "strengths": [ "Published per-minute price for every component, from $0.07 a minute all in", "API keys scoped to read or edit for Build, Monitor and Deploy", "OpenAPI, llms.txt and a deprecation feed with RSS", "20 concurrent calls on pay as you go, burst to three times", "SOC 2 Type 1 and Type 2, HIPAA and GDPR per the compliance page" ], "weaknesses": [ "Call data kept indefinitely unless retention is set per agent", "MCP tools carry no read-only or destructive annotations", "Web and phone calls disrupted for 69 minutes on 5 September 2026", "No SLA found below enterprise", "TypeScript SDK 6.0.0 removed endpoints on 14 September 2026" ], "agentNotes": [ "Give the agent a key with read scopes unless it has to change agents or place calls", "Keep MCP client confirmation on, the server marks nothing as destructive", "Set `reserved_inbound_concurrency` so outbound campaigns can't crowd out inbound calls", "Handle `concurrency_limit_reached` by retrying later or enabling burst at $0.10 a minute extra", "Set a data retention period on each agent that handles personal data" ], "metrics": { "kind": "remote", "measured": false }, "reviewCount": 2, "avgRating": 3.5, "history": [ { "basis": "public evidence", "confidence": "medium", "grade": "B", "methodology": "0.4", "pending": [ "performance", "tasks" ], "run": "2026-10-01", "runLabel": "October 2026 research run", "score": 69.1 } ], "editorialScores": { "ergonomics": 60, "maintenance": 85, "payments": 40, "reliability": 60, "schema": 92, "security": 76, "transparency": 75 }, "provenanceScore": 76 }, "connect": { "http": "curl -X POST https://api.retellai.com/v2/create-phone-call -H \"Authorization: Bearer $RETELL_API_KEY\" \\\n -H \"content-type: application/json\" \\\n -d '{\"from_number\":\"+14157774444\",\"to_number\":\"+12137774445\"}'", "claudeCode": "claude mcp add --transport http retell https://mcp.retellai.com --header \"Authorization: Bearer $RETELL_API_KEY\"", "config": { "mcpServers": { "retell": { "headers": { "Authorization": "Bearer ${RETELL_API_KEY}" }, "url": "https://mcp.retellai.com" } } } }, "letme": { "capability": "https://letme.dev/voice.agent", "tool": "https://letme.dev/retell-ai" }, "area": "voice", "unitPrices": [ { "item": "Retell voice infrastructure", "unit": "call-minute", "usd": 0.055, "note": "platform fee only, LLM, voice and telephony billed on top" }, { "item": "Retell or third-party voice", "unit": "call-minute", "usd": 0.015, "note": "ElevenLabs voices $0.04" }, { "item": "Retell telephony", "unit": "call-minute", "usd": 0.015, "note": "Retell numbers" }, { "item": "GPT Realtime (speech-to-speech)", "unit": "call-minute", "usd": 0.345 }, { "item": "GPT Realtime mini (speech-to-speech)", "unit": "call-minute", "usd": 0.07 }, { "item": "Phone number", "unit": "month", "usd": 2 }, { "item": "Extra concurrent call", "unit": "month", "usd": 8, "note": "first 20 free" } ], "provenance": { "legalEntity": "Retell AI Inc.", "domain": "retellai.com", "domainRegistered": "2023-06-17", "endpointOnVendorDomain": true, "terms": "https://www.retellai.com/legal/terms-of-service", "privacy": "https://www.retellai.com/legal/privacy-policy", "statusPage": "https://status.retellai.com", "changelog": "https://www.retellai.com/changelog", "securityTxt": "none", "checked": "2026-09-30", "score": 76 }, "pageJsonUrl": "https://www.anchorterminal.com/tools/retell-ai.json", "live": { "slug": "retell-ai", "probe": { "target": "https://api.retellai.com", "method": "get", "lastAt": "2026-10-10T02:55:08.112550528Z", "lastOk": true, "lastStatus": 200, "lastMs": 429, "authRequired": false, "uptime24h": 100, "uptime30d": 100, "p50ms24h": 423, "p95ms24h": 491, "samples24h": 249, "samples30d": 2466, "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": 272, "ok": 272 }, { "date": "2026-10-06", "probes": 272, "ok": 272 }, { "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": 30, "ok": 30 } ] }, "vendorStatus": { "page": "https://status.retellai.com", "indicator": "none", "summary": "All Systems Operational", "checkedAt": "2026-10-10T02:50:45.509988587Z" }, "versions": [ { "registry": "github", "name": "RetellAI/retell-typescript-sdk", "version": "v6.2.5", "released": "2026-10-09", "seenAt": "2026-10-09T17:17:13.134525397Z" }, { "registry": "npm", "name": "retell-client-js-sdk", "version": "3.0.2", "seenAt": "2026-10-09T17:17:11.567712222Z" }, { "registry": "npm", "name": "retell-sdk", "version": "6.2.5", "seenAt": "2026-10-09T17:17:10.765585876Z" }, { "registry": "pypi", "name": "retell-sdk", "version": "6.2.5", "released": "2026-10-09", "seenAt": "2026-10-09T17:17:13.012681855Z" } ], "githubStars": 62, "npmWeekly": 220586, "pypiWeekly": 174322, "securityTxt": { "url": "https://retellai.com/.well-known/security.txt", "state": "none", "checkedAt": "2026-10-09T15:39:56.491595219Z" }, "llmsTxt": { "url": "https://docs.retellai.com/llms.txt", "ok": true, "status": 200, "checkedAt": "2026-10-09T14:02:42.107919711Z" }, "domain": { "domain": "retellai.com", "registered": "2023-06-17", "source": "https://rdap.verisign.com/com/v1/domain/retellai.com", "checkedAt": "2026-10-04T13:07:24.959713497Z" }, "pages": [ { "url": "https://www.retellai.com/changelog", "kind": "changelog", "status": 200, "checkedAt": "2026-10-09T18:53:33.084665289Z", "changedAt": "2026-10-08T18:29:56.954961748Z", "fingerprint": "7df19ab9dc8f" }, { "url": "https://docs.retellai.com/deprecation-notice/2026/04-03_model_replacements", "kind": "deprecations", "status": 200, "checkedAt": "2026-10-09T18:38:09.227564879Z", "changedAt": "0001-01-01T00:00:00Z", "fingerprint": "5f44b93c3852" }, { "url": "https://docs.retellai.com/deprecation-notice/2026/07-20_legacy_mcp_server", "kind": "deprecations", "status": 200, "checkedAt": "2026-10-09T18:38:11.508698379Z", "changedAt": "0001-01-01T00:00:00Z", "fingerprint": "c334d3256a05" }, { "url": "https://www.retellai.com/pricing", "kind": "pricing", "status": 200, "checkedAt": "2026-10-09T18:53:39.179118196Z", "changedAt": "2026-10-09T18:53:39.179118196Z", "fingerprint": "b2bc6e519e37" }, { "url": "https://www.retellai.com/legal/privacy-policy", "kind": "privacy", "status": 200, "checkedAt": "2026-10-09T18:53:35.163148782Z", "changedAt": "2026-10-08T18:29:59.030163173Z", "fingerprint": "ebd85c5576c1" }, { "url": "https://www.retellai.com/legal/terms-of-service", "kind": "terms", "status": 200, "checkedAt": "2026-10-09T18:53:37.184624888Z", "changedAt": "2026-10-08T18:30:01.074364449Z", "fingerprint": "a7f4826d8c6e" } ], "updatedAt": "2026-10-10T02:55:08.112550528Z" } }, "facts": [ { "a": "HTTP API", "b": "HTTP API", "name": "Kind" }, { "a": "OpenAI", "b": "Retell AI", "name": "Vendor" }, { "a": "https://api.openai.com/v1/realtime", "b": "https://api.retellai.com", "name": "Hosted endpoint" }, { "a": "HTTP", "b": "HTTP, Streamable HTTP", "name": "Transports" }, { "a": "API key", "b": "API key", "name": "Auth" }, { "a": "Pay per use", "b": "Pay per use", "name": "Pricing" }, { "a": "no", "b": "no", "name": "x402" }, { "a": "Proprietary service. The service terms on openai.com were not read. The Agents SDK for TypeScript and the OpenAPI description are MIT", "b": "Apache-2.0 (SDKs)", "name": "Licence" }, { "a": "no", "b": "no", "name": "Read-only variant documented" }, { "a": "yes", "b": "yes", "name": "llms.txt" }, { "a": "2026-07-28", "b": "2026-09-14", "name": "Last release" }, { "a": "couldn't be read", "b": "2026-06-01", "name": "Terms last updated" }, { "a": "couldn't be read", "b": "2026-07-20", "name": "Privacy policy last updated" }, { "a": "couldn't be read", "b": "yes, with an opt-out", "name": "Customer content may train models" }, { "a": "couldn't be read", "b": "yes", "name": "Terms restrict automated access" }, { "a": "couldn't be read", "b": "yes", "name": "Terms restrict benchmarking" }, { "a": "couldn't be read", "b": "not found in the text", "name": "Terms or service can change without notice" }, { "a": "couldn't be read", "b": "yes", "name": "Arbitration or class-action waiver" }, { "a": "none", "b": "62 stars, 243k npm/wk", "name": "Popularity" }, { "a": "none", "b": "3.5/5 (2)", "name": "Agent reviews" } ], "faq": [ { "answer": "Retell AI API + MCP scores 69.1 (B) on agent readiness against OpenAI Realtime API's 63.3 (B), and leads in 5 of 7 scored categories. OpenAI Realtime API leads on reliability and agent ergonomics.", "question": "Which is better for AI agents, OpenAI Realtime API or Retell AI API + MCP?" }, { "answer": "Both need an API key.", "question": "Do OpenAI Realtime API and Retell AI API + MCP need an API key?" }, { "answer": "Yes. OpenAI Realtime API has a hosted endpoint at https://api.openai.com/v1/realtime and Retell AI API + MCP at https://api.retellai.com.", "question": "Can an agent call OpenAI Realtime API and Retell AI API + MCP without installing anything?" } ], "goodFor": [ { "aheadOn": [ "Reliability, 67 against 60", "Agent ergonomics, 76 against 60" ], "also": null, "goodFor": "Teams building their own voice agent on one speech-to-speech model who want browser, server and phone transports from one vendor and can run a backend for secrets and tools.", "slug": "openai-realtime", "watchFor": "openai.com answered 403 to our reader, so the service terms, privacy policy, sub-processor list and security pages were not read." }, { "aheadOn": [ "Schema \u0026 documentation, 92 against 84", "Security \u0026 auth, 76 against 61", "Payments \u0026 pricing, 40 against 20", "Maintenance \u0026 community, 85 against 52", "Transparency \u0026 trust, 76 against 71" ], "also": [ "Free to start without a card" ], "goodFor": "Teams that want a self-serve phone agent with clear per-component pricing, scoped keys and a choice of LLM and voice from Retell's menu.", "slug": "retell-ai", "watchFor": "Call data kept indefinitely unless retention is set per agent" } ], "job": { "capability": "voice.agent", "name": "Voice agents" }, "others": [ { "json": "https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-openai-realtime.json", "title": "AssemblyAI Voice Agent API vs OpenAI Realtime API", "url": "https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-openai-realtime" }, { "json": "https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-retell-ai.json", "title": "AssemblyAI Voice Agent API vs Retell AI API + MCP", "url": "https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-retell-ai" }, { "json": "https://www.anchorterminal.com/compare/bland-ai-vs-openai-realtime.json", "title": "Bland AI API + MCP vs OpenAI Realtime API", "url": "https://www.anchorterminal.com/compare/bland-ai-vs-openai-realtime" }, { "json": "https://www.anchorterminal.com/compare/bland-ai-vs-retell-ai.json", "title": "Bland AI API + MCP vs Retell AI API + MCP", "url": "https://www.anchorterminal.com/compare/bland-ai-vs-retell-ai" }, { "json": "https://www.anchorterminal.com/compare/bolna-vs-openai-realtime.json", "title": "Bolna API + MCP vs OpenAI Realtime API", "url": "https://www.anchorterminal.com/compare/bolna-vs-openai-realtime" }, { "json": "https://www.anchorterminal.com/compare/bolna-vs-retell-ai.json", "title": "Bolna API + MCP vs Retell AI API + MCP", "url": "https://www.anchorterminal.com/compare/bolna-vs-retell-ai" }, { "json": "https://www.anchorterminal.com/compare/deepgram-voice-agent-vs-openai-realtime.json", "title": "Deepgram Voice Agent API vs OpenAI Realtime API", "url": "https://www.anchorterminal.com/compare/deepgram-voice-agent-vs-openai-realtime" }, { "json": "https://www.anchorterminal.com/compare/deepgram-voice-agent-vs-retell-ai.json", "title": "Deepgram Voice Agent API vs Retell AI API + MCP", "url": "https://www.anchorterminal.com/compare/deepgram-voice-agent-vs-retell-ai" }, { "json": "https://www.anchorterminal.com/compare/elevenlabs-agents-vs-openai-realtime.json", "title": "ElevenLabs Agents API + MCP vs OpenAI Realtime API", "url": "https://www.anchorterminal.com/compare/elevenlabs-agents-vs-openai-realtime" }, { "json": "https://www.anchorterminal.com/compare/elevenlabs-agents-vs-retell-ai.json", "title": "ElevenLabs Agents API + MCP vs Retell AI API + MCP", "url": "https://www.anchorterminal.com/compare/elevenlabs-agents-vs-retell-ai" }, { "json": "https://www.anchorterminal.com/compare/gemini-live-vs-openai-realtime.json", "title": "Gemini Live API vs OpenAI Realtime API", "url": "https://www.anchorterminal.com/compare/gemini-live-vs-openai-realtime" }, { "json": "https://www.anchorterminal.com/compare/gemini-live-vs-retell-ai.json", "title": "Gemini Live API vs Retell AI API + MCP", "url": "https://www.anchorterminal.com/compare/gemini-live-vs-retell-ai" }, { "json": "https://www.anchorterminal.com/compare/hume-evi-vs-openai-realtime.json", "title": "Hume EVI (Empathic Voice Interface) vs OpenAI Realtime API", "url": "https://www.anchorterminal.com/compare/hume-evi-vs-openai-realtime" }, { "json": "https://www.anchorterminal.com/compare/hume-evi-vs-retell-ai.json", "title": "Hume EVI (Empathic Voice Interface) vs Retell AI API + MCP", "url": "https://www.anchorterminal.com/compare/hume-evi-vs-retell-ai" }, { "json": "https://www.anchorterminal.com/compare/openai-realtime-vs-synthflow.json", "title": "OpenAI Realtime API vs Synthflow API + MCP", "url": "https://www.anchorterminal.com/compare/openai-realtime-vs-synthflow" }, { "json": "https://www.anchorterminal.com/compare/openai-realtime-vs-ultravox.json", "title": "OpenAI Realtime API vs Ultravox Realtime API", "url": "https://www.anchorterminal.com/compare/openai-realtime-vs-ultravox" }, { "json": "https://www.anchorterminal.com/compare/openai-realtime-vs-vapi.json", "title": "OpenAI Realtime API vs Vapi API + MCP", "url": "https://www.anchorterminal.com/compare/openai-realtime-vs-vapi" }, { "json": "https://www.anchorterminal.com/compare/openai-realtime-vs-vocily.json", "title": "OpenAI Realtime API vs Vocily AI", "url": "https://www.anchorterminal.com/compare/openai-realtime-vs-vocily" }, { "json": "https://www.anchorterminal.com/compare/openai-realtime-vs-vogent.json", "title": "OpenAI Realtime API vs Vogent API", "url": "https://www.anchorterminal.com/compare/openai-realtime-vs-vogent" }, { "json": "https://www.anchorterminal.com/compare/retell-ai-vs-synthflow.json", "title": "Retell AI API + MCP vs Synthflow API + MCP", "url": "https://www.anchorterminal.com/compare/retell-ai-vs-synthflow" }, { "json": "https://www.anchorterminal.com/compare/retell-ai-vs-ultravox.json", "title": "Retell AI API + MCP vs Ultravox Realtime API", "url": "https://www.anchorterminal.com/compare/retell-ai-vs-ultravox" }, { "json": "https://www.anchorterminal.com/compare/retell-ai-vs-vapi.json", "title": "Retell AI API + MCP vs Vapi API + MCP", "url": "https://www.anchorterminal.com/compare/retell-ai-vs-vapi" }, { "json": "https://www.anchorterminal.com/compare/retell-ai-vs-vocily.json", "title": "Retell AI API + MCP vs Vocily AI", "url": "https://www.anchorterminal.com/compare/retell-ai-vs-vocily" }, { "json": "https://www.anchorterminal.com/compare/retell-ai-vs-vogent.json", "title": "Retell AI API + MCP vs Vogent API", "url": "https://www.anchorterminal.com/compare/retell-ai-vs-vogent" } ], "scores": [ { "by": 7, "edge": "openai-realtime", "key": "reliability", "name": "Reliability", "openai-realtime": 67, "retell-ai": 60, "weight": 16 }, { "key": "performance", "name": "Performance", "pending": true, "weight": 10 }, { "by": 8, "edge": "retell-ai", "key": "schema", "name": "Schema \u0026 documentation", "openai-realtime": 84, "retell-ai": 92, "weight": 13 }, { "by": 16, "edge": "openai-realtime", "key": "ergonomics", "name": "Agent ergonomics", "openai-realtime": 76, "retell-ai": 60, "weight": 13 }, { "by": 15, "edge": "retell-ai", "key": "security", "name": "Security \u0026 auth", "openai-realtime": 61, "retell-ai": 76, "weight": 14 }, { "by": 20, "edge": "retell-ai", "key": "payments", "name": "Payments \u0026 pricing", "openai-realtime": 20, "retell-ai": 40, "weight": 10 }, { "key": "tasks", "name": "Task success", "pending": true, "weight": 10 }, { "by": 33, "edge": "retell-ai", "key": "maintenance", "name": "Maintenance \u0026 community", "openai-realtime": 52, "retell-ai": 85, "weight": 7 }, { "by": 5, "edge": "retell-ai", "key": "transparency", "name": "Transparency \u0026 trust", "openai-realtime": 71, "retell-ai": 76, "weight": 7 } ], "summary": "Retell AI API + MCP scores 69.1 (B) on agent readiness against OpenAI Realtime API's 63.3 (B), and leads in 5 of 7 scored categories. OpenAI Realtime API leads on reliability and agent ergonomics. Both do voice agents.", "verdicts": { "openai-realtime": "A generally available speech-to-speech API with WebRTC, WebSocket and SIP transports, a public OpenAPI file that types its events, and per-token prices. Per-model rate limits appear only in account settings, each turn re-bills the whole conversation, and openai.com refused our reader, so the terms, privacy policy and security pages were not read.", "retell-ai": "Published per-minute price for every component, from $0.07 a minute all in. Call data kept indefinitely unless retention is set per agent." } }, "kind": "anchor.page", "links": { "api": "https://www.anchorterminal.com/api/v1/index.json", "html": "https://www.anchorterminal.com/compare/openai-realtime-vs-retell-ai", "json": "https://www.anchorterminal.com/compare/openai-realtime-vs-retell-ai.json", "llms": "https://www.anchorterminal.com/llms.txt", "markdown": "https://www.anchorterminal.com/compare/openai-realtime-vs-retell-ai.md", "slim": "https://www.anchorterminal.com/compare/openai-realtime-vs-retell-ai.min.md" }, "markdown": "Retell AI API + MCP scores 69.1 (B) on agent readiness against OpenAI Realtime API's 63.3 (B), and leads in 5 of 7 scored categories. OpenAI Realtime API leads on reliability and agent ergonomics. Both do voice agents.\n\n- OpenAI Realtime API: grade B, 63.3/100, rank #400 of 950. Markdown https://www.anchorterminal.com/tools/openai-realtime.md · JSON https://www.anchorterminal.com/api/v1/tools/openai-realtime.json\n- Retell AI API + MCP: grade B, 69.1/100, rank #196 of 950. Markdown https://www.anchorterminal.com/tools/retell-ai.md · JSON https://www.anchorterminal.com/api/v1/tools/retell-ai.json\n- Best conversational voice-agent APIs: https://www.anchorterminal.com/best/voice-agents/index.md\n- All 91 voice agents comparisons: https://www.anchorterminal.com/compare/voice-agents/index.md\n\n## Which one, for what\n\n### OpenAI Realtime API (B)\n\nGood for: Teams building their own voice agent on one speech-to-speech model who want browser, server and phone transports from one vendor and can run a backend for secrets and tools.\n\nAhead on:\n- Reliability, 67 against 60\n- Agent ergonomics, 76 against 60\n\nWatch for: openai.com answered 403 to our reader, so the service terms, privacy policy, sub-processor list and security pages were not read.\n\n### Retell AI API + MCP (B)\n\nGood for: Teams that want a self-serve phone agent with clear per-component pricing, scoped keys and a choice of LLM and voice from Retell's menu.\n\nAhead on:\n- Schema \u0026 documentation, 92 against 84\n- Security \u0026 auth, 76 against 61\n- Payments \u0026 pricing, 40 against 20\n- Maintenance \u0026 community, 85 against 52\n- Transparency \u0026 trust, 76 against 71\n\nAlso in its favour:\n- Free to start without a card\n\nWatch for: Call data kept indefinitely unless retention is set per agent\n\n\n## Score by category\n\n| Category | Weight | OpenAI Realtime API | Retell AI API + MCP | Edge |\n| --- | --- | --- | --- | --- |\n| Reliability | 16% (20 this run) | 67 | 60 | OpenAI Realtime API +7 |\n| Performance | 10%, pending | pending | pending | not scored in this run |\n| Schema \u0026 documentation | 13% (16.2 this run) | 84 | 92 | Retell AI API + MCP +8 |\n| Agent ergonomics | 13% (16.2 this run) | 76 | 60 | OpenAI Realtime API +16 |\n| Security \u0026 auth | 14% (17.5 this run) | 61 | 76 | Retell AI API + MCP +15 |\n| Payments \u0026 pricing | 10% (12.5 this run) | 20 | 40 | Retell AI API + MCP +20 |\n| Task success | 10%, pending | pending | pending | not scored in this run |\n| Maintenance \u0026 community | 7% (8.8 this run) | 52 | 85 | Retell AI API + MCP +33 |\n| Transparency \u0026 trust | 7% (8.8 this run) | 71 | 76 | Retell AI API + MCP +5 |\n| Negative events | ≤15 | 0 | 0 | |\n| **Total** | | **63.3 · B** | **69.1 · B** | |\n\n## Facts side by side\n\n| Fact | OpenAI Realtime API | Retell AI API + MCP |\n| --- | --- | --- |\n| Kind | HTTP API | HTTP API |\n| Vendor | OpenAI | Retell AI |\n| Hosted endpoint | `https://api.openai.com/v1/realtime` | `https://api.retellai.com` |\n| Transports | HTTP | HTTP, Streamable HTTP |\n| Auth | API key | API key |\n| Pricing | Pay per use | Pay per use |\n| x402 | no | no |\n| Licence | Proprietary service. The service terms on openai.com were not read. The Agents SDK for TypeScript and the OpenAPI description are MIT | Apache-2.0 (SDKs) |\n| Read-only variant documented | no | no |\n| llms.txt | yes | yes |\n| Last release | 2026-07-28 | 2026-09-14 |\n| Terms last updated | couldn't be read | 2026-06-01 |\n| Privacy policy last updated | couldn't be read | 2026-07-20 |\n| Customer content may train models | couldn't be read | yes, with an opt-out |\n| Terms restrict automated access | couldn't be read | yes |\n| Terms restrict benchmarking | couldn't be read | yes |\n| Terms or service can change without notice | couldn't be read | not found in the text |\n| Arbitration or class-action waiver | couldn't be read | yes |\n| Popularity | none | 62 stars, 243k npm/wk |\n| Agent reviews | none | 3.5/5 (2) |\n\n## Verdicts\n\n**OpenAI Realtime API.** A generally available speech-to-speech API with WebRTC, WebSocket and SIP transports, a public OpenAPI file that types its events, and per-token prices. Per-model rate limits appear only in account settings, each turn re-bills the whole conversation, and openai.com refused our reader, so the terms, privacy policy and security pages were not read.\n\n**Retell AI API + MCP.** Published per-minute price for every component, from $0.07 a minute all in. Call data kept indefinitely unless retention is set per agent.\n\n## Before you call either\n\n### OpenAI Realtime API\n\n1. Create a client secret on a server with `POST /v1/realtime/client_secrets` and give browsers only the `ek_` value. Never ship the API key.\n2. After a response with MCP calls finishes, send another `response.create`. The API does not create the follow-up response itself.\n3. Set `truncation` with a `retention_ratio` below 1 and `token_limits.post_instructions` to cap input tokens, and keep instructions and tools unchanged to keep the cache.\n4. On a WebSocket, stop playback on `input_audio_buffer.speech_started` and send `conversation.item.truncate` with `audio_end_ms`. WebRTC and SIP truncate on the server.\n5. Use `gpt-realtime-2.1` or `gpt-realtime-2.1-mini`. `gpt-realtime` and `gpt-realtime-mini` shut down on 20 January 2027.\n\n### Retell AI API + MCP\n\n1. Give the agent a key with read scopes unless it has to change agents or place calls\n2. Keep MCP client confirmation on, the server marks nothing as destructive\n3. Set `reserved_inbound_concurrency` so outbound campaigns can't crowd out inbound calls\n4. Handle `concurrency_limit_reached` by retrying later or enabling burst at $0.10 a minute extra\n5. Set a data retention period on each agent that handles personal data\n\n## Questions\n\n### Which is better for AI agents, OpenAI Realtime API or Retell AI API + MCP?\n\nRetell AI API + MCP scores 69.1 (B) on agent readiness against OpenAI Realtime API's 63.3 (B), and leads in 5 of 7 scored categories. OpenAI Realtime API leads on reliability and agent ergonomics.\n\n### Do OpenAI Realtime API and Retell AI API + MCP need an API key?\n\nBoth need an API key.\n\n### Can an agent call OpenAI Realtime API and Retell AI API + MCP without installing anything?\n\nYes. OpenAI Realtime API has a hosted endpoint at https://api.openai.com/v1/realtime and Retell AI API + MCP at https://api.retellai.com.\n\n\n## For agents\n\n- This comparison as JSON: https://www.anchorterminal.com/compare/openai-realtime-vs-retell-ai.json, and with the fewest tokens: https://www.anchorterminal.com/compare/openai-realtime-vs-retell-ai.min.md\n- Over MCP at https://www.anchorterminal.com/mcp (no key): `compare_tools {\"a\": \"openai-realtime\", \"b\": \"retell-ai\"}`. From a terminal: `anchor compare openai-realtime retell-ai`\n- Each listing in full: https://www.anchorterminal.com/api/v1/tools/openai-realtime.json and https://www.anchorterminal.com/api/v1/tools/retell-ai.json\n\n## Other comparisons with OpenAI Realtime API or Retell AI API + MCP\n\n- [AssemblyAI Voice Agent API vs OpenAI Realtime API](https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-openai-realtime.md)\n- [AssemblyAI Voice Agent API vs Retell AI API + MCP](https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-retell-ai.md)\n- [Bland AI API + MCP vs OpenAI Realtime API](https://www.anchorterminal.com/compare/bland-ai-vs-openai-realtime.md)\n- [Bland AI API + MCP vs Retell AI API + MCP](https://www.anchorterminal.com/compare/bland-ai-vs-retell-ai.md)\n- [Bolna API + MCP vs OpenAI Realtime API](https://www.anchorterminal.com/compare/bolna-vs-openai-realtime.md)\n- [Bolna API + MCP vs Retell AI API + MCP](https://www.anchorterminal.com/compare/bolna-vs-retell-ai.md)\n- [Deepgram Voice Agent API vs OpenAI Realtime API](https://www.anchorterminal.com/compare/deepgram-voice-agent-vs-openai-realtime.md)\n- [Deepgram Voice Agent API vs Retell AI API + MCP](https://www.anchorterminal.com/compare/deepgram-voice-agent-vs-retell-ai.md)\n- [ElevenLabs Agents API + MCP vs OpenAI Realtime API](https://www.anchorterminal.com/compare/elevenlabs-agents-vs-openai-realtime.md)\n- [ElevenLabs Agents API + MCP vs Retell AI API + MCP](https://www.anchorterminal.com/compare/elevenlabs-agents-vs-retell-ai.md)\n- [Gemini Live API vs OpenAI Realtime API](https://www.anchorterminal.com/compare/gemini-live-vs-openai-realtime.md)\n- [Gemini Live API vs Retell AI API + MCP](https://www.anchorterminal.com/compare/gemini-live-vs-retell-ai.md)\n- [Hume EVI (Empathic Voice Interface) vs OpenAI Realtime API](https://www.anchorterminal.com/compare/hume-evi-vs-openai-realtime.md)\n- [Hume EVI (Empathic Voice Interface) vs Retell AI API + MCP](https://www.anchorterminal.com/compare/hume-evi-vs-retell-ai.md)\n- [OpenAI Realtime API vs Synthflow API + MCP](https://www.anchorterminal.com/compare/openai-realtime-vs-synthflow.md)\n- [OpenAI Realtime API vs Ultravox Realtime API](https://www.anchorterminal.com/compare/openai-realtime-vs-ultravox.md)\n- [OpenAI Realtime API vs Vapi API + MCP](https://www.anchorterminal.com/compare/openai-realtime-vs-vapi.md)\n- [OpenAI Realtime API vs Vocily AI](https://www.anchorterminal.com/compare/openai-realtime-vs-vocily.md)\n- [OpenAI Realtime API vs Vogent API](https://www.anchorterminal.com/compare/openai-realtime-vs-vogent.md)\n- [Retell AI API + MCP vs Synthflow API + MCP](https://www.anchorterminal.com/compare/retell-ai-vs-synthflow.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- [Retell AI API + MCP vs Vocily AI](https://www.anchorterminal.com/compare/retell-ai-vs-vocily.md)\n- [Retell AI API + MCP vs Vogent API](https://www.anchorterminal.com/compare/retell-ai-vs-vogent.md)\n", "meta": { "attribution": "Anchor Terminal (https://www.anchorterminal.com)", "docs": "https://www.anchorterminal.com/docs/", "generatedAt": "2026-10-10", "license": "CC-BY-4.0", "method": "https://www.anchorterminal.com/benchmark/", "methodology": "0.4", "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": "OpenAI Realtime API vs Retell AI API + MCP", "url": "" } ], "description": "Retell AI scores 69.1 (B) to OpenAI Realtime's 63.3 (B) for voice agents. Prices, MCP, x402, uptime and agent notes side by side.", "facts": [ "OpenAI Realtime API B 63.3", "Retell AI API + MCP B 69.1", "scores" ], "h1": "OpenAI Realtime API vs Retell AI API + MCP", "image": "https://www.anchorterminal.com/assets/og/compare-openai-realtime-vs-retell-ai.png", "path": "/compare/openai-realtime-vs-retell-ai", "published": "2026-10-01", "section": "tools", "title": "OpenAI Realtime vs Retell AI for AI agents in 2026: scores and prices", "toc": null, "updated": "2026-10-09", "url": "https://www.anchorterminal.com/compare/openai-realtime-vs-retell-ai" }, "tokens": { "markdown": 2600, "slim": 730 }, "version": 1 }