{
  "data": {
    "a": {
      "slug": "assemblyai-voice-agent",
      "name": "AssemblyAI Voice Agent API",
      "vendor": "AssemblyAI, Inc.",
      "vendorUrl": "https://www.assemblyai.com",
      "kind": "http-api",
      "category": "voice-agents",
      "summary": "AssemblyAI's Voice Agent API runs a spoken conversation over one WebSocket, combining its own speech-to-text, language model and text-to-speech. Agents are stored through a REST API and reached from a browser, a server or an inbound Twilio SIP number.",
      "url": "https://www.anchorterminal.com/tools/assemblyai-voice-agent",
      "markdownUrl": "https://www.anchorterminal.com/tools/assemblyai-voice-agent.md",
      "slimMarkdownUrl": "https://www.anchorterminal.com/tools/assemblyai-voice-agent.min.md",
      "jsonUrl": "https://www.anchorterminal.com/api/v1/tools/assemblyai-voice-agent.json",
      "repo": "https://github.com/AssemblyAI/voice-agent-starter-python",
      "license": "Proprietary service under AssemblyAI's Terms of Service. The two starter repositories on GitHub carry no licence file",
      "transports": [
        "http"
      ],
      "remoteUrl": "wss://agents.assemblyai.com/v1/ws",
      "packages": [],
      "auth": "api-key",
      "authNotes": "Self-serve API key from the dashboard, sent in the `Authorization` header on REST calls and on the WebSocket upgrade, with or without a `Bearer` prefix. Keys belong to a project and can be created and deleted in the dashboard (2 on the free plan, 4 on pay as you go, 25 on a contract). No scopes or expiry were found. Browser clients use a one-time token from `GET /v1/token`, redeemable within 1 to 600 seconds and passed as the `token` query parameter.",
      "pricing": "usage",
      "pricingNotes": "$4.50 an hour ($0.075 a minute), billed per second from socket open to session end, idle time included. The rate covers speech-to-text, the managed model, speech output, recordings and hosting. New accounts get $50 of credit with no card, which covers the Voice Agent API. LLM Gateway tokens and Twilio carrier minutes are billed separately. Volume pricing is by sales contact (https://www.assemblyai.com/pricing, https://www.assemblyai.com/docs/billing-and-pricing, checked 2026-10-09).",
      "priceSummary": "Pay per use",
      "where": "hosted",
      "x402": {
        "level": "no",
        "evidence": "No x402, MPP or L402 in the Voice Agent docs, the two API description files, the billing docs or the pricing page. Payment is by card into a prepaid balance (checked 2026-10-09).",
        "endpoints": []
      },
      "toolCount": null,
      "popularity": {
        "githubStars": null,
        "npmWeekly": null,
        "pypiWeekly": null,
        "asOf": "2026-10-09"
      },
      "docsUrl": "https://www.assemblyai.com/docs/voice-agents/voice-agent-api",
      "llmsTxt": "https://www.assemblyai.com/docs/llms.txt",
      "openapi": "https://www.assemblyai.com/docs/api-reference/specs/voice-agent-api.yaml",
      "capabilities": [
        "voice.agent",
        "voice.pipeline",
        "voice.tools",
        "voice.telephony"
      ],
      "tags": [
        "hosted",
        "no-card",
        "closed-source",
        "llms-txt",
        "webhooks",
        "streaming",
        "pipeline",
        "python",
        "javascript",
        "status-page",
        "soc2"
      ],
      "lastRelease": "2026-08-26",
      "graded": true,
      "anchor": {
        "graded": true,
        "score": 64.4,
        "grade": "B",
        "agentReady": false,
        "rank": 351,
        "ranked": true,
        "rankOf": 950,
        "categoryRank": 4,
        "methodology": "0.4",
        "run": "2026-10-01",
        "scores": {
          "ergonomics": 72,
          "maintenance": 64,
          "payments": 40,
          "reliability": 60,
          "schema": 83,
          "security": 62,
          "transparency": 66
        },
        "pending": [
          "performance",
          "tasks"
        ],
        "assessment": {
          "confidence": "medium",
          "date": "2026-10-09"
        },
        "negative": 0,
        "verdict": "One $0.075 a minute rate covers speech-to-text, the managed model, speech output, recordings and hosting, and the socket has an AsyncAPI file, typed error codes and a 30-second resume window. No concurrent-session limit is published, the status page has no Voice Agent component, and phone calls are inbound only through a Twilio trunk the customer owns.",
        "bestFor": "A developer who wants one managed pipeline at a flat rate and is content with AssemblyAI's own speech models and voices, with an optional model of their own.",
        "strengths": [
          "One published rate of $4.50 an hour ($0.075 a minute), billed per second, with $50 of credit and no card for new accounts",
          "AsyncAPI 3.0 file for the socket, an OpenAPI file for the token endpoint, llms.txt and a Markdown copy of every docs page",
          "Session errors carry a code, a message and sometimes the offending field, and the docs name the three codes that are safe to retry",
          "HTTP tool header values are write-only and encrypted at rest, and tool calls are limited to public `https` hosts with redirects refused",
          "Every session is stored with a stereo recording, a JSON timeline of turns and tool calls, and signed webhooks with a delivery history"
        ],
        "weaknesses": [
          "No number is published for the concurrent-session limit that the `concurrency_exceeded` error enforces",
          "status.assemblyai.com lists the Asynchronous API, Streaming API and LLM Gateway, with no Voice Agent component",
          "Telephony is inbound only, over a SIP trunk on a Twilio account the customer owns",
          "API keys have no scopes or expiry, and opting out of model training needs a paid plan",
          "The Terms of Service bar benchmarking and competitive analysis (2.4(f)) and any automated or programmatic method of extracting data or Output (4.4), which matters before any probe is run"
        ],
        "agentNotes": [
          "Send `session.end` before closing the socket. Without it the session stays resumable, and billed, for 30 seconds",
          "Retry only `at_capacity`, `concurrency_exceeded` and `internal_error`, with backoff. Every other session error code is fatal",
          "Send `tool.result` inside the `reply.done` handler, not straight after `tool.call`",
          "Mint a one-time token with `GET /v1/token` for browser clients and never ship the API key to a page",
          "Deduplicate webhooks on `event_id`, and verify `X-AAI-Signature` against the raw body bytes because a 401 is not retried"
        ],
        "metrics": {
          "kind": "remote",
          "measured": false
        },
        "reviewCount": 0,
        "avgRating": 0,
        "history": [
          {
            "basis": "public evidence",
            "confidence": "medium",
            "grade": "B",
            "methodology": "0.4",
            "pending": [
              "performance",
              "tasks"
            ],
            "run": "2026-10-01",
            "runLabel": "October 2026 research run",
            "score": 64.4
          }
        ],
        "editorialScores": {
          "ergonomics": 72,
          "maintenance": 64,
          "payments": 40,
          "reliability": 60,
          "schema": 83,
          "security": 62,
          "transparency": 51
        },
        "provenanceScore": 81
      },
      "connect": {
        "install": "git clone https://github.com/AssemblyAI/voice-agent-starter-python",
        "http": "curl -X POST https://agents.assemblyai.com/v1/agents \\\n  -H \"Authorization: $ASSEMBLYAI_API_KEY\" \\\n  -H \"Content-Type: application/json\" \\\n  -d '{\"name\": \"Support Assistant\", \"system_prompt\": \"You are a friendly support agent.\", \"greeting\": \"Hi, how can I help?\", \"voice\": {\"voice_id\": \"alba\"}}'",
        "claudeCode": "claude mcp add --transport http --scope user assemblyai-docs https://mcp.assemblyai.com/docs"
      },
      "letme": {
        "capability": "https://letme.dev/voice.agent",
        "tool": "https://letme.dev/assemblyai-voice-agent"
      },
      "sameCompany": [
        "assemblyai-stt"
      ],
      "area": "voice",
      "unitPrices": [
        {
          "item": "Voice Agent session",
          "unit": "call-minute",
          "usd": 0.075,
          "note": "$4.50 an hour billed per second of open socket. Speech-to-text, managed model, speech output and recordings included. LLM Gateway tokens and carrier minutes extra"
        }
      ],
      "provenance": {
        "legalEntity": "AssemblyAI, Inc.",
        "domain": "assemblyai.com",
        "domainRegistered": "2016-12-24",
        "endpointOnVendorDomain": true,
        "terms": "https://www.assemblyai.com/legal/terms-of-service",
        "privacy": "https://www.assemblyai.com/legal/privacy-policy",
        "statusPage": "https://status.assemblyai.com",
        "changelog": "https://www.assemblyai.com/changelog",
        "securityTxt": "unknown",
        "checked": "2026-10-09",
        "score": 81
      },
      "pageJsonUrl": "https://www.anchorterminal.com/tools/assemblyai-voice-agent.json",
      "live": {
        "slug": "assemblyai-voice-agent",
        "probe": {
          "target": "wss://agents.assemblyai.com/v1/ws",
          "method": "get",
          "lastAt": "2026-10-10T04:40:41.250040088Z",
          "lastOk": false,
          "lastStatus": 0,
          "lastMs": 0,
          "lastNote": "unsupported protocol scheme \"wss\"",
          "authRequired": false,
          "uptime24h": 0,
          "uptime30d": 0,
          "p50ms24h": 0,
          "p95ms24h": 0,
          "samples24h": 133,
          "samples30d": 133,
          "days": [
            {
              "date": "2026-10-09",
              "probes": 85,
              "ok": 0
            },
            {
              "date": "2026-10-10",
              "probes": 48,
              "ok": 0
            }
          ],
          "outages": [
            {
              "start": "2026-10-09T15:42:56.660671906Z",
              "end": "0001-01-01T00:00:00Z",
              "note": "unsupported protocol scheme \"wss\""
            }
          ]
        },
        "vendorStatus": {
          "page": "https://status.assemblyai.com",
          "indicator": "none",
          "summary": "All Systems Operational",
          "checkedAt": "2026-10-10T04:40:42.447340051Z"
        },
        "githubStars": 3,
        "pages": [
          {
            "url": "https://www.assemblyai.com/docs/billing-and-pricing",
            "kind": "pricing",
            "status": 200,
            "checkedAt": "2026-10-09T18:48:16.435584974Z",
            "changedAt": "0001-01-01T00:00:00Z",
            "fingerprint": "3b80ad9644cf"
          }
        ],
        "updatedAt": "2026-10-10T04:40:41.250040088Z"
      }
    },
    "answer": "AssemblyAI Voice Agent API and Vapi API + MCP score within a point of each other on agent readiness, 64.4 (B) and 63.5 (B). Vapi API + MCP leads on reliability, schema \u0026 documentation, maintenance \u0026 community and transparency \u0026 trust.",
    "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": 63.5,
        "grade": "B",
        "agentReady": false,
        "rank": 390,
        "ranked": true,
        "rankOf": 950,
        "categoryRank": 6,
        "methodology": "0.4",
        "run": "2026-10-01",
        "scores": {
          "ergonomics": 64,
          "maintenance": 88,
          "payments": 35,
          "reliability": 70,
          "schema": 89,
          "security": 58,
          "transparency": 73
        },
        "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.",
        "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, 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": "0.4",
            "pending": [
              "performance",
              "tasks"
            ],
            "run": "2026-10-01",
            "runLabel": "October 2026 research run",
            "score": 63.5
          }
        ],
        "editorialScores": {
          "ergonomics": 64,
          "maintenance": 88,
          "payments": 35,
          "reliability": 70,
          "schema": 89,
          "security": 58,
          "transparency": 70
        },
        "provenanceScore": 76
      },
      "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": 76
      },
      "pageJsonUrl": "https://www.anchorterminal.com/tools/vapi.json",
      "live": {
        "slug": "vapi",
        "probe": {
          "target": "https://api.vapi.ai",
          "method": "get",
          "lastAt": "2026-10-10T04:41:07.923367827Z",
          "lastOk": true,
          "lastStatus": 200,
          "lastMs": 181,
          "authRequired": false,
          "uptime24h": 100,
          "uptime30d": 100,
          "p50ms24h": 205,
          "p95ms24h": 744,
          "samples24h": 248,
          "samples30d": 2484,
          "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": 48,
              "ok": 48
            }
          ]
        },
        "vendorStatus": {
          "page": "https://status.vapi.ai",
          "indicator": "unknown",
          "summary": "no machine-readable status found",
          "checkedAt": "2026-10-10T00:51:22.534980323Z"
        },
        "versions": [
          {
            "registry": "github",
            "name": "VapiAI/mcp-server",
            "version": "v0.0.11",
            "released": "2026-08-14",
            "seenAt": "2026-10-09T17:26:37.035713479Z"
          },
          {
            "registry": "npm",
            "name": "@vapi-ai/mcp-server",
            "version": "0.0.11",
            "seenAt": "2026-10-09T17:26:35.22504936Z"
          },
          {
            "registry": "npm",
            "name": "@vapi-ai/server-sdk",
            "version": "2.0.1",
            "seenAt": "2026-10-09T17:26:31.845046246Z"
          },
          {
            "registry": "npm",
            "name": "@vapi-ai/web",
            "version": "2.7.1",
            "seenAt": "2026-10-09T17:26:33.654793058Z"
          },
          {
            "registry": "pypi",
            "name": "vapi_server_sdk",
            "version": "1.11.1",
            "released": "2026-05-20",
            "seenAt": "2026-10-09T17:26:35.041883091Z"
          }
        ],
        "githubStars": 57,
        "npmWeekly": 165652,
        "pypiWeekly": 46392,
        "securityTxt": {
          "url": "https://vapi.ai/.well-known/security.txt",
          "state": "none",
          "checkedAt": "2026-10-09T15:40:30.151900047Z"
        },
        "llmsTxt": {
          "url": "https://docs.vapi.ai/llms.txt",
          "ok": true,
          "status": 200,
          "checkedAt": "2026-10-09T14:02:57.845010485Z"
        },
        "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": 304,
            "checkedAt": "2026-10-09T18:38:40.486035241Z",
            "changedAt": "2026-10-08T18:19:42.551636345Z",
            "fingerprint": "ccc854cf802d"
          },
          {
            "url": "https://docs.vapi.ai/whats-new",
            "kind": "changelog",
            "status": 200,
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        "updatedAt": "2026-10-10T04:41:07.923367827Z"
      }
    },
    "facts": [
      {
        "a": "HTTP API",
        "b": "HTTP API",
        "name": "Kind"
      },
      {
        "a": "AssemblyAI, Inc.",
        "b": "Vapi",
        "name": "Vendor"
      },
      {
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        "b": "https://api.vapi.ai",
        "name": "Hosted endpoint"
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        "a": "HTTP",
        "b": "HTTP, Streamable HTTP, stdio",
        "name": "Transports"
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        "a": "API key",
        "b": "API key",
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        "a": "Pay per use",
        "b": "Pay per use",
        "name": "Pricing"
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      {
        "a": "$0.075 per minute of call",
        "b": "not published",
        "name": "Price for voice agents"
      },
      {
        "a": "no",
        "b": "no",
        "name": "x402"
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      {
        "a": "Proprietary service under AssemblyAI's Terms of Service. The two starter repositories on GitHub carry no licence file",
        "b": "MIT (MCP server)",
        "name": "Licence"
      },
      {
        "a": "none",
        "b": "20",
        "name": "Tools exposed"
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      {
        "a": "no",
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        "a": "2026-05-26",
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        "name": "Privacy policy last updated"
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      {
        "a": "yes, with an opt-out",
        "b": "yes",
        "name": "Customer content may train models"
      },
      {
        "a": "yes",
        "b": "yes",
        "name": "Terms restrict automated access"
      },
      {
        "a": "yes",
        "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"
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      {
        "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": "AssemblyAI Voice Agent API and Vapi API + MCP score within a point of each other on agent readiness, 64.4 (B) and 63.5 (B). Vapi API + MCP leads on reliability, schema \u0026 documentation, maintenance \u0026 community and transparency \u0026 trust.",
        "question": "Which is better for AI agents, AssemblyAI Voice Agent API or Vapi API + MCP?"
      },
      {
        "answer": "Both need an API key.",
        "question": "Do AssemblyAI Voice Agent API and Vapi API + MCP need an API key?"
      },
      {
        "answer": "Yes. AssemblyAI Voice Agent API has a hosted endpoint at wss://agents.assemblyai.com/v1/ws and Vapi API + MCP at https://api.vapi.ai.",
        "question": "Can an agent call AssemblyAI Voice Agent API and Vapi API + MCP without installing anything?"
      }
    ],
    "goodFor": [
      {
        "aheadOn": [
          "Agent ergonomics, 72 against 64",
          "Payments \u0026 pricing, 40 against 35"
        ],
        "also": [
          "No incidents deducted, where Vapi API + MCP loses 4 points for them"
        ],
        "goodFor": "A developer who wants one managed pipeline at a flat rate and is content with AssemblyAI's own speech models and voices, with an optional model of their own.",
        "slug": "assemblyai-voice-agent",
        "watchFor": "No number is published for the concurrent-session limit that the `concurrency_exceeded` error enforces"
      },
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        "aheadOn": [
          "Reliability, 70 against 60",
          "Schema \u0026 documentation, 89 against 83",
          "Maintenance \u0026 community, 88 against 64",
          "Transparency \u0026 trust, 73 against 66"
        ],
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          "Runs on your own machine"
        ],
        "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"
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        "json": "https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-elevenlabs-agents.json",
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        "json": "https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-hume-evi.json",
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        "json": "https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-openai-realtime.json",
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        "json": "https://www.anchorterminal.com/compare/gemini-live-vs-vapi.json",
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        "url": "https://www.anchorterminal.com/compare/gemini-live-vs-vapi"
      },
      {
        "json": "https://www.anchorterminal.com/compare/hume-evi-vs-vapi.json",
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        "json": "https://www.anchorterminal.com/compare/retell-ai-vs-vapi.json",
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      },
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        "url": "https://www.anchorterminal.com/compare/vapi-vs-vogent"
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    "scores": [
      {
        "assemblyai-voice-agent": 60,
        "by": 10,
        "edge": "vapi",
        "key": "reliability",
        "name": "Reliability",
        "vapi": 70,
        "weight": 16
      },
      {
        "key": "performance",
        "name": "Performance",
        "pending": true,
        "weight": 10
      },
      {
        "assemblyai-voice-agent": 83,
        "by": 6,
        "edge": "vapi",
        "key": "schema",
        "name": "Schema \u0026 documentation",
        "vapi": 89,
        "weight": 13
      },
      {
        "assemblyai-voice-agent": 72,
        "by": 8,
        "edge": "assemblyai-voice-agent",
        "key": "ergonomics",
        "name": "Agent ergonomics",
        "vapi": 64,
        "weight": 13
      },
      {
        "assemblyai-voice-agent": 62,
        "by": 4,
        "edge": "assemblyai-voice-agent",
        "key": "security",
        "name": "Security \u0026 auth",
        "vapi": 58,
        "weight": 14
      },
      {
        "assemblyai-voice-agent": 40,
        "by": 5,
        "edge": "assemblyai-voice-agent",
        "key": "payments",
        "name": "Payments \u0026 pricing",
        "vapi": 35,
        "weight": 10
      },
      {
        "key": "tasks",
        "name": "Task success",
        "pending": true,
        "weight": 10
      },
      {
        "assemblyai-voice-agent": 64,
        "by": 24,
        "edge": "vapi",
        "key": "maintenance",
        "name": "Maintenance \u0026 community",
        "vapi": 88,
        "weight": 7
      },
      {
        "assemblyai-voice-agent": 66,
        "by": 7,
        "edge": "vapi",
        "key": "transparency",
        "name": "Transparency \u0026 trust",
        "vapi": 73,
        "weight": 7
      }
    ],
    "summary": "AssemblyAI Voice Agent API and Vapi API + MCP score within a point of each other on agent readiness, 64.4 (B) and 63.5 (B). Vapi API + MCP leads on reliability, schema \u0026 documentation, maintenance \u0026 community and transparency \u0026 trust. Both do voice agents.",
    "verdicts": {
      "assemblyai-voice-agent": "One $0.075 a minute rate covers speech-to-text, the managed model, speech output, recordings and hosting, and the socket has an AsyncAPI file, typed error codes and a 30-second resume window. No concurrent-session limit is published, the status page has no Voice Agent component, and phone calls are inbound only through a Twilio trunk the customer owns.",
      "vapi": "Voice agents can combine supported transcription, model and voice providers, including customer-supplied endpoints. Per-minute cost depends on the selected providers."
    }
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  "markdown": "AssemblyAI Voice Agent API and Vapi API + MCP score within a point of each other on agent readiness, 64.4 (B) and 63.5 (B). Vapi API + MCP leads on reliability, schema \u0026 documentation, maintenance \u0026 community and transparency \u0026 trust. Both do voice agents.\n\n- AssemblyAI Voice Agent API: grade B, 64.4/100, rank #351 of 950. Markdown https://www.anchorterminal.com/tools/assemblyai-voice-agent.md · JSON https://www.anchorterminal.com/api/v1/tools/assemblyai-voice-agent.json\n- Vapi API + MCP: grade B, 63.5/100, rank #390 of 950. 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 91 voice agents comparisons: https://www.anchorterminal.com/compare/voice-agents/index.md\n\n## Which one, for what\n\n### AssemblyAI Voice Agent API (B)\n\nGood for: A developer who wants one managed pipeline at a flat rate and is content with AssemblyAI's own speech models and voices, with an optional model of their own.\n\nAhead on:\n- Agent ergonomics, 72 against 64\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 number is published for the concurrent-session limit that the `concurrency_exceeded` error enforces\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 60\n- Schema \u0026 documentation, 89 against 83\n- Maintenance \u0026 community, 88 against 64\n- Transparency \u0026 trust, 73 against 66\n\nAlso in its favour:\n- Runs on your own machine\n\nWatch for: Real per-minute cost depends on provider choices\n\n\n## Score by category\n\n| Category | Weight | AssemblyAI Voice Agent API | Vapi API + MCP | Edge |\n| --- | --- | --- | --- | --- |\n| Reliability | 16% (20 this run) | 60 | 70 | Vapi API + MCP +10 |\n| Performance | 10%, pending | pending | pending | not scored in this run |\n| Schema \u0026 documentation | 13% (16.2 this run) | 83 | 89 | Vapi API + MCP +6 |\n| Agent ergonomics | 13% (16.2 this run) | 72 | 64 | AssemblyAI Voice Agent API +8 |\n| Security \u0026 auth | 14% (17.5 this run) | 62 | 58 | AssemblyAI Voice Agent API +4 |\n| Payments \u0026 pricing | 10% (12.5 this run) | 40 | 35 | AssemblyAI Voice Agent API +5 |\n| Task success | 10%, pending | pending | pending | not scored in this run |\n| Maintenance \u0026 community | 7% (8.8 this run) | 64 | 88 | Vapi API + MCP +24 |\n| Transparency \u0026 trust | 7% (8.8 this run) | 66 | 73 | Vapi API + MCP +7 |\n| Negative events | ≤15 | 0 | -4 | |\n| **Total** | | **64.4 · B** | **63.5 · B** | |\n\n## Facts side by side\n\n| Fact | AssemblyAI Voice Agent API | Vapi API + MCP |\n| --- | --- | --- |\n| Kind | HTTP API | HTTP API |\n| Vendor | AssemblyAI, Inc. | Vapi |\n| Hosted endpoint | `wss://agents.assemblyai.com/v1/ws` | `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| Price for voice agents | $0.075 per minute of call | not published |\n| x402 | no | no |\n| Licence | Proprietary service under AssemblyAI's Terms of Service. The two starter repositories on GitHub carry no licence file | MIT (MCP server) |\n| Tools exposed | none | 20 |\n| Read-only variant documented | no | no |\n| llms.txt | yes | yes |\n| Last release | 2026-08-26 | 2026-09-21 |\n| Terms last updated | 2026-07-01 | 2026-09-14 |\n| Privacy policy last updated | 2026-05-26 | 2023-09-09 |\n| Customer content may train models | yes, with an opt-out | yes |\n| Terms restrict automated access | yes | yes |\n| Terms restrict benchmarking | yes | 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## Verdicts\n\n**AssemblyAI Voice Agent API.** One $0.075 a minute rate covers speech-to-text, the managed model, speech output, recordings and hosting, and the socket has an AsyncAPI file, typed error codes and a 30-second resume window. No concurrent-session limit is published, the status page has no Voice Agent component, and phone calls are inbound only through a Twilio trunk the customer owns.\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### AssemblyAI Voice Agent API\n\n1. Send `session.end` before closing the socket. Without it the session stays resumable, and billed, for 30 seconds\n2. Retry only `at_capacity`, `concurrency_exceeded` and `internal_error`, with backoff. Every other session error code is fatal\n3. Send `tool.result` inside the `reply.done` handler, not straight after `tool.call`\n4. Mint a one-time token with `GET /v1/token` for browser clients and never ship the API key to a page\n5. Deduplicate webhooks on `event_id`, and verify `X-AAI-Signature` against the raw body bytes because a 401 is not retried\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## Questions\n\n### Which is better for AI agents, AssemblyAI Voice Agent API or Vapi API + MCP?\n\nAssemblyAI Voice Agent API and Vapi API + MCP score within a point of each other on agent readiness, 64.4 (B) and 63.5 (B). Vapi API + MCP leads on reliability, schema \u0026 documentation, maintenance \u0026 community and transparency \u0026 trust.\n\n### Do AssemblyAI Voice Agent API and Vapi API + MCP need an API key?\n\nBoth need an API key.\n\n### Can an agent call AssemblyAI Voice Agent API and Vapi API + MCP without installing anything?\n\nYes. AssemblyAI Voice Agent API has a hosted endpoint at wss://agents.assemblyai.com/v1/ws and Vapi API + MCP at https://api.vapi.ai.\n\n\n## For agents\n\n- This comparison as JSON: https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-vapi.json, and with the fewest tokens: https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-vapi.min.md\n- Over MCP at https://www.anchorterminal.com/mcp (no key): `compare_tools {\"a\": \"assemblyai-voice-agent\", \"b\": \"vapi\"}`. From a terminal: `anchor compare assemblyai-voice-agent vapi`\n- Each listing in full: https://www.anchorterminal.com/api/v1/tools/assemblyai-voice-agent.json and https://www.anchorterminal.com/api/v1/tools/vapi.json\n\n## Other comparisons with AssemblyAI Voice Agent API or Vapi API + MCP\n\n- [AssemblyAI Voice Agent API vs Bland AI API + MCP](https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-bland-ai.md)\n- [AssemblyAI Voice Agent API vs Bolna API + MCP](https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-bolna.md)\n- [AssemblyAI Voice Agent API vs Deepgram Voice Agent API](https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-deepgram-voice-agent.md)\n- [AssemblyAI Voice Agent API vs ElevenLabs Agents API + MCP](https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-elevenlabs-agents.md)\n- [AssemblyAI Voice Agent API vs Gemini Live API](https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-gemini-live.md)\n- [AssemblyAI Voice Agent API vs Hume EVI (Empathic Voice Interface)](https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-hume-evi.md)\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- [AssemblyAI Voice Agent API vs Synthflow API + MCP](https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-synthflow.md)\n- [AssemblyAI Voice Agent API vs Ultravox Realtime API](https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-ultravox.md)\n- [AssemblyAI Voice Agent API vs Vocily AI](https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-vocily.md)\n- [AssemblyAI Voice Agent API vs Vogent API](https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-vogent.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 Vapi API + MCP](https://www.anchorterminal.com/compare/bolna-vs-vapi.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 Vapi API + MCP](https://www.anchorterminal.com/compare/elevenlabs-agents-vs-vapi.md)\n- [Gemini Live API vs Vapi API + MCP](https://www.anchorterminal.com/compare/gemini-live-vs-vapi.md)\n- [Hume EVI (Empathic Voice Interface) vs Vapi API + MCP](https://www.anchorterminal.com/compare/hume-evi-vs-vapi.md)\n- [OpenAI Realtime API vs Vapi API + MCP](https://www.anchorterminal.com/compare/openai-realtime-vs-vapi.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 Vapi API + MCP](https://www.anchorterminal.com/compare/synthflow-vs-vapi.md)\n- [Ultravox Realtime API vs Vapi API + MCP](https://www.anchorterminal.com/compare/ultravox-vs-vapi.md)\n- [Vapi API + MCP vs Vocily AI](https://www.anchorterminal.com/compare/vapi-vs-vocily.md)\n- [Vapi API + MCP vs Vogent API](https://www.anchorterminal.com/compare/vapi-vs-vogent.md)\n",
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