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          "note": "first 20 free"
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    "answer": "Retell AI API + MCP scores 69.2 (B) on agent readiness against Rime Prism's 57.9 (C), and leads in 5 of 7 scored categories. Rime Prism leads on agent ergonomics.",
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      "url": "https://www.anchorterminal.com/tools/rime-prism",
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      "auth": "api-key",
      "authNotes": "Rime API key from the dashboard, sent as `Authorization: Bearer` on the WebSocket upgrade from a backend. Prism reads no query parameters, so the key can't go in the URL, and it has no ephemeral tokens for browsers or phones. The same key covers Rime's text-to-speech and speech-to-text. No scoped or read-only keys were found in the docs.",
      "pricing": "freemium",
      "pricingNotes": "$0.08 a minute of call audio on Flex (pay as you go, card billed monthly) and $0.064 on Scale ($100 a month of credit, 20% off). Every account gets $50 of usage a month across Rime's models, Prism included, with no card. Fine-tuning, custom voices, VPC or on-prem deployment, SLAs and a BAA are Enterprise items with custom pricing (https://www.rime.ai/pricing, checked 2026-10-28).",
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      "x402": {
        "level": "no",
        "evidence": "No x402, MPP or L402 in the Prism docs, the API reference or the pricing page, checked 2026-10-28. Paid plans bill a card monthly.",
        "endpoints": []
      },
      "toolCount": null,
      "popularity": {
        "githubStars": null,
        "npmWeekly": null,
        "pypiWeekly": null,
        "asOf": "2026-10-28"
      },
      "docsUrl": "https://docs.rime.ai/docs/prism/overview",
      "llmsTxt": "https://docs.rime.ai/llms.txt",
      "capabilities": [
        "voice.speech-to-speech",
        "voice.agent",
        "voice.tools"
      ],
      "tags": [
        "hosted",
        "freemium",
        "no-card",
        "free-tier",
        "closed-source",
        "speech-to-speech",
        "websocket",
        "streaming",
        "function-calling",
        "llms-txt",
        "python",
        "typescript",
        "go",
        "rust",
        "status-page",
        "soc2",
        "hipaa",
        "enterprise"
      ],
      "lastRelease": "2026-10-28",
      "graded": true,
      "anchor": {
        "graded": true,
        "score": 57.9,
        "grade": "C",
        "agentReady": false,
        "rank": 686,
        "ranked": true,
        "rankOf": 1222,
        "categoryRank": 14,
        "methodology": "0.7",
        "run": "2026-10-01",
        "scores": {
          "ergonomics": 73,
          "maintenance": 65,
          "payments": 40,
          "reliability": 41,
          "schema": 69,
          "security": 56,
          "transparency": 70
        },
        "pending": [
          "performance",
          "tasks"
        ],
        "assessment": {
          "confidence": "medium",
          "date": "2026-10-28"
        },
        "negative": 0,
        "verdict": "Prism's WebSocket API is well documented for a launch-day product, with typed events, 41 error codes that say what to do and a published per-minute price with free monthly usage. It has no Prism component or history on Rime's status page, no published concurrency limit, alpha SDKs, English only, and no data-handling statement that covers caller audio.",
        "bestFor": "English voice agents on Rime's cloud that want one speech-to-speech model with their own tools, and teams moving an OpenAI Realtime beta client who can bridge phone audio themselves.",
        "strengths": [
          "Errors page lists 41 codes, each with scope, the field at fault, a correlation ID and what to do",
          "$0.08 a minute on Flex, with $50 of free usage a month and no card",
          "Uses OpenAI Realtime beta event names, with a migration guide for WebSocket, LiveKit, Pipecat and OpenAI SDK clients",
          "Key only in the upgrade header, and Prism reads no query parameters",
          "Context truncation is configurable and each reply reports what was left out and its token usage"
        ],
        "weaknesses": [
          "Rime's status page had no Prism component on launch day, and there is no incident history for it",
          "No concurrency limit per account or key was found, and a full server refuses with 503",
          "All four SDKs are 0.1.0 alpha releases that may change their API",
          "English only, four voices, 16 kHz PCM16 in, with no mu-law, so phone calls need a bridge",
          "Privacy and security pages describe text in, audio out, and say nothing specific about caller audio"
        ],
        "agentNotes": [
          "Connect from a backend with `Authorization: Bearer`, since Prism has no browser tokens and reads no query parameters.",
          "Send `session.update` before any audio, or every append fails with `session_not_initialized`.",
          "Keep streaming audio, silence included, while Prism speaks, because it finds turn ends and interruptions from that audio.",
          "Ask for the continuation after each tool result, since Prism doesn't resume on its own, and never rerun a call with an unknown outcome.",
          "Pin the exact SDK version, because the SDKs are alpha and a new release can change the API."
        ],
        "metrics": {
          "kind": "remote",
          "measured": false
        },
        "reviewCount": 0,
        "avgRating": 0,
        "history": [
          {
            "basis": "public evidence",
            "confidence": "medium",
            "grade": "C",
            "methodology": "0.7",
            "pending": [
              "performance",
              "tasks"
            ],
            "run": "2026-10-01",
            "runLabel": "October 2026 research run",
            "score": 57.9
          }
        ],
        "editorialScores": {
          "ergonomics": 73,
          "maintenance": 65,
          "payments": 40,
          "reliability": 41,
          "schema": 69,
          "security": 56,
          "transparency": 58
        },
        "provenanceScore": 81,
        "checked": {
          "categories": {
            "ergonomics": "2026-10-28",
            "maintenance": "2026-10-28",
            "payments": "2026-10-28",
            "reliability": "2026-10-28",
            "schema": "2026-10-28",
            "security": "2026-10-28",
            "transparency": "2026-10-28"
          },
          "last": "2026-10-28",
          "oldest": "2026-10-28",
          "stale": false,
          "staleAfterDays": 90
        }
      },
      "connect": {
        "install": "uv add \"rimelabs-sdk==0.1.0a25\""
      },
      "letme": {
        "capability": "https://letme.dev/voice.speech-to-speech",
        "tool": "https://letme.dev/rime-prism"
      },
      "sameCompany": [
        "rime-tts"
      ],
      "area": "voice",
      "unitPrices": [
        {
          "item": "Prism, Flex",
          "unit": "call-minute",
          "usd": 0.08,
          "note": "Metered by the minute of call audio, pay as you go. Pricing page, checked 28 October 2026"
        },
        {
          "item": "Prism, Scale",
          "unit": "call-minute",
          "usd": 0.064,
          "note": "20% off Flex for $100 a month of credit, which rolls over up to $200. Pricing page, checked 28 October 2026"
        }
      ],
      "provenance": {
        "legalEntity": "Rime Labs, Inc.",
        "domain": "rime.ai",
        "domainRegistered": "2020-03-12",
        "endpointOnVendorDomain": true,
        "terms": "https://www.rime.ai/terms",
        "privacy": "https://www.rime.ai/privacy",
        "statusPage": "https://www.rimestat.us",
        "changelog": "https://docs.rime.ai/docs/changelog",
        "securityTxt": "none",
        "checked": "2026-10-28",
        "notes": [
          "The terms name Rime Labs, Inc., the same entity as the rime-tts listing. The domain registration date stands per that listing's check of 30 September 2026 and wasn't re-read.",
          "status.rime.ai redirects to www.rimestat.us, an incident.io page with Text-to-speech API and Platform API components and data since 30 August 2026. It had no Prism component on 28 October 2026.",
          "www.rime.ai/.well-known/security.txt answered 404. The security page links a vulnerability disclosure policy.",
          "The Prism endpoint is on prism.api.rime.ai, under the vendor's own domain."
        ],
        "score": 81
      },
      "pageJsonUrl": "https://www.anchorterminal.com/tools/rime-prism.json",
      "live": {
        "slug": "rime-prism",
        "probe": {
          "target": "wss://prism.api.rime.ai/v1/realtime",
          "method": "get",
          "lastAt": "2026-10-29T20:41:25.616992818Z",
          "lastOk": false,
          "lastStatus": 0,
          "lastMs": 0,
          "lastNote": "unsupported protocol scheme \"wss\"",
          "authRequired": false,
          "uptime24h": 0,
          "uptime30d": 0,
          "p50ms24h": 0,
          "p95ms24h": 0,
          "samples24h": 36,
          "samples30d": 36,
          "days": [
            {
              "date": "2026-10-29",
              "probes": 36,
              "ok": 0
            }
          ],
          "outages": [
            {
              "start": "2026-10-29T17:19:57.075096127Z",
              "end": "0001-01-01T00:00:00Z",
              "note": "unsupported protocol scheme \"wss\""
            }
          ]
        },
        "vendorStatus": {
          "page": "https://www.rimestat.us",
          "indicator": "none",
          "summary": "All Systems Operational",
          "checkedAt": "2026-10-29T20:31:37.377251634Z"
        },
        "updatedAt": "2026-10-29T20:41:25.616992818Z"
      }
    },
    "facts": [
      {
        "a": "HTTP API",
        "b": "HTTP API",
        "name": "Kind"
      },
      {
        "a": "Retell AI",
        "b": "Rime Labs",
        "name": "Vendor"
      },
      {
        "a": "https://api.retellai.com",
        "b": "wss://prism.api.rime.ai/v1/realtime",
        "name": "Hosted endpoint"
      },
      {
        "a": "HTTP, Streamable HTTP",
        "b": "websocket",
        "name": "Transports"
      },
      {
        "a": "API key",
        "b": "API key",
        "name": "Auth"
      },
      {
        "a": "Pay per use",
        "b": "Freemium",
        "name": "Pricing"
      },
      {
        "a": "no",
        "b": "no",
        "name": "x402"
      },
      {
        "a": "Apache-2.0 (SDKs)",
        "b": "Proprietary hosted service under Rime's terms. The Rime SDK used to call it (github.com/rimelabs/rime-sdk) is MIT.",
        "name": "Licence"
      },
      {
        "a": "no",
        "b": "no",
        "name": "Read-only variant documented"
      },
      {
        "a": "yes",
        "b": "yes",
        "name": "llms.txt"
      },
      {
        "a": "2026-09-14",
        "b": "2026-10-28",
        "name": "Last release"
      },
      {
        "a": "2026-06-01",
        "b": "no date given",
        "name": "Terms last updated"
      },
      {
        "a": "2026-07-20",
        "b": "no date given",
        "name": "Privacy policy last updated"
      },
      {
        "a": "yes, with an opt-out",
        "b": "not found in the text",
        "name": "Customer content may train models"
      },
      {
        "a": "yes",
        "b": "not found in the text",
        "name": "Terms restrict automated access"
      },
      {
        "a": "yes",
        "b": "yes",
        "name": "Terms restrict benchmarking"
      },
      {
        "a": "not found in the text",
        "b": "not found in the text",
        "name": "Terms or service can change without notice"
      },
      {
        "a": "yes",
        "b": "yes",
        "name": "Arbitration or class-action waiver"
      },
      {
        "a": "62 stars, 243k npm/wk",
        "b": "none",
        "name": "Popularity"
      },
      {
        "a": "3.5/5 (2)",
        "b": "none",
        "name": "Agent reviews"
      }
    ],
    "faq": [
      {
        "answer": "Retell AI API + MCP scores 69.2 (B) on agent readiness against Rime Prism's 57.9 (C), and leads in 5 of 7 scored categories. Rime Prism leads on agent ergonomics.",
        "question": "Which is better for AI agents, Retell AI API + MCP or Rime Prism?"
      },
      {
        "answer": "Both need an API key.",
        "question": "Do Retell AI API + MCP and Rime Prism need an API key?"
      },
      {
        "answer": "Yes. Retell AI API + MCP has a hosted endpoint at https://api.retellai.com and Rime Prism at wss://prism.api.rime.ai/v1/realtime.",
        "question": "Can an agent call Retell AI API + MCP and Rime Prism without installing anything?"
      }
    ],
    "goodFor": [
      {
        "aheadOn": [
          "Reliability, 60 against 41",
          "Schema \u0026 documentation, 92 against 69",
          "Security \u0026 auth, 76 against 56",
          "Maintenance \u0026 community, 85 against 65",
          "Transparency \u0026 trust, 77 against 70"
        ],
        "also": null,
        "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"
      },
      {
        "aheadOn": [
          "Agent ergonomics, 73 against 60"
        ],
        "also": null,
        "goodFor": "English voice agents on Rime's cloud that want one speech-to-speech model with their own tools, and teams moving an OpenAI Realtime beta client who can bridge phone audio themselves.",
        "slug": "rime-prism",
        "watchFor": "Rime's status page had no Prism component on launch day, and there is no incident history for it"
      }
    ],
    "job": {
      "capability": "voice.agent",
      "name": "Voice agents"
    },
    "others": [
      {
        "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/assemblyai-voice-agent-vs-rime-prism.json",
        "title": "AssemblyAI Voice Agent API vs Rime Prism",
        "url": "https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-rime-prism"
      },
      {
        "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/bland-ai-vs-rime-prism.json",
        "title": "Bland AI API + MCP vs Rime Prism",
        "url": "https://www.anchorterminal.com/compare/bland-ai-vs-rime-prism"
      },
      {
        "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/bolna-vs-rime-prism.json",
        "title": "Bolna API + MCP vs Rime Prism",
        "url": "https://www.anchorterminal.com/compare/bolna-vs-rime-prism"
      },
      {
        "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/deepgram-voice-agent-vs-rime-prism.json",
        "title": "Deepgram Voice Agent API vs Rime Prism",
        "url": "https://www.anchorterminal.com/compare/deepgram-voice-agent-vs-rime-prism"
      },
      {
        "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/elevenlabs-agents-vs-rime-prism.json",
        "title": "ElevenLabs Agents API + MCP vs Rime Prism",
        "url": "https://www.anchorterminal.com/compare/elevenlabs-agents-vs-rime-prism"
      },
      {
        "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/gemini-live-vs-rime-prism.json",
        "title": "Gemini Live API vs Rime Prism",
        "url": "https://www.anchorterminal.com/compare/gemini-live-vs-rime-prism"
      },
      {
        "json": "https://www.anchorterminal.com/compare/harmony-ai-vs-retell-ai.json",
        "title": "Harmony.ai vs Retell AI API + MCP",
        "url": "https://www.anchorterminal.com/compare/harmony-ai-vs-retell-ai"
      },
      {
        "json": "https://www.anchorterminal.com/compare/harmony-ai-vs-rime-prism.json",
        "title": "Harmony.ai vs Rime Prism",
        "url": "https://www.anchorterminal.com/compare/harmony-ai-vs-rime-prism"
      },
      {
        "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/hume-evi-vs-rime-prism.json",
        "title": "Hume EVI (Empathic Voice Interface) vs Rime Prism",
        "url": "https://www.anchorterminal.com/compare/hume-evi-vs-rime-prism"
      },
      {
        "json": "https://www.anchorterminal.com/compare/livekit-agents-vs-retell-ai.json",
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        "url": "https://www.anchorterminal.com/compare/livekit-agents-vs-retell-ai"
      },
      {
        "json": "https://www.anchorterminal.com/compare/livekit-agents-vs-rime-prism.json",
        "title": "LiveKit Agents vs Rime Prism",
        "url": "https://www.anchorterminal.com/compare/livekit-agents-vs-rime-prism"
      },
      {
        "json": "https://www.anchorterminal.com/compare/openai-realtime-vs-retell-ai.json",
        "title": "OpenAI Realtime API vs Retell AI API + MCP",
        "url": "https://www.anchorterminal.com/compare/openai-realtime-vs-retell-ai"
      },
      {
        "json": "https://www.anchorterminal.com/compare/openai-realtime-vs-rime-prism.json",
        "title": "OpenAI Realtime API vs Rime Prism",
        "url": "https://www.anchorterminal.com/compare/openai-realtime-vs-rime-prism"
      },
      {
        "json": "https://www.anchorterminal.com/compare/pipecat-vs-retell-ai.json",
        "title": "Pipecat vs Retell AI API + MCP",
        "url": "https://www.anchorterminal.com/compare/pipecat-vs-retell-ai"
      },
      {
        "json": "https://www.anchorterminal.com/compare/pipecat-vs-rime-prism.json",
        "title": "Pipecat vs Rime Prism",
        "url": "https://www.anchorterminal.com/compare/pipecat-vs-rime-prism"
      },
      {
        "json": "https://www.anchorterminal.com/compare/placecall-vs-retell-ai.json",
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      {
        "json": "https://www.anchorterminal.com/compare/placecall-vs-rime-prism.json",
        "title": "PlaceCall vs Rime Prism",
        "url": "https://www.anchorterminal.com/compare/placecall-vs-rime-prism"
      },
      {
        "json": "https://www.anchorterminal.com/compare/retell-ai-vs-synthflow.json",
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        "url": "https://www.anchorterminal.com/compare/retell-ai-vs-synthflow"
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      {
        "json": "https://www.anchorterminal.com/compare/retell-ai-vs-ultravox.json",
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        "url": "https://www.anchorterminal.com/compare/retell-ai-vs-ultravox"
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        "url": "https://www.anchorterminal.com/compare/retell-ai-vs-vapi"
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        "json": "https://www.anchorterminal.com/compare/retell-ai-vs-vocily.json",
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        "url": "https://www.anchorterminal.com/compare/retell-ai-vs-vocily"
      },
      {
        "json": "https://www.anchorterminal.com/compare/retell-ai-vs-vogent.json",
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        "url": "https://www.anchorterminal.com/compare/retell-ai-vs-vogent"
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      {
        "json": "https://www.anchorterminal.com/compare/rime-prism-vs-synthflow.json",
        "title": "Rime Prism vs Synthflow API + MCP",
        "url": "https://www.anchorterminal.com/compare/rime-prism-vs-synthflow"
      },
      {
        "json": "https://www.anchorterminal.com/compare/rime-prism-vs-vocily.json",
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        "url": "https://www.anchorterminal.com/compare/rime-prism-vs-vocily"
      },
      {
        "json": "https://www.anchorterminal.com/compare/rime-prism-vs-vogent.json",
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        "url": "https://www.anchorterminal.com/compare/rime-prism-vs-vogent"
      },
      {
        "json": "https://www.anchorterminal.com/compare/cuelight-vs-retell-ai.json",
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        "url": "https://www.anchorterminal.com/compare/cuelight-vs-retell-ai"
      },
      {
        "json": "https://www.anchorterminal.com/compare/pipecat-phonellm-vs-retell-ai.json",
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        "url": "https://www.anchorterminal.com/compare/pipecat-phonellm-vs-retell-ai"
      },
      {
        "json": "https://www.anchorterminal.com/compare/gpt-live-vs-retell-ai.json",
        "title": "GPT-Live vs Retell AI API + MCP",
        "url": "https://www.anchorterminal.com/compare/gpt-live-vs-retell-ai"
      },
      {
        "json": "https://www.anchorterminal.com/compare/gpt-live-vs-rime-prism.json",
        "title": "GPT-Live vs Rime Prism",
        "url": "https://www.anchorterminal.com/compare/gpt-live-vs-rime-prism"
      },
      {
        "json": "https://www.anchorterminal.com/compare/rime-prism-vs-ultravox.json",
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        "url": "https://www.anchorterminal.com/compare/rime-prism-vs-ultravox"
      },
      {
        "json": "https://www.anchorterminal.com/compare/rime-prism-vs-vapi.json",
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        "url": "https://www.anchorterminal.com/compare/rime-prism-vs-vapi"
      },
      {
        "json": "https://www.anchorterminal.com/compare/pipecat-phonellm-vs-rime-prism.json",
        "title": "Pipecat PhoneLLM vs Rime Prism",
        "url": "https://www.anchorterminal.com/compare/pipecat-phonellm-vs-rime-prism"
      }
    ],
    "scores": [
      {
        "by": 19,
        "edge": "retell-ai",
        "key": "reliability",
        "name": "Reliability",
        "retell-ai": 60,
        "rime-prism": 41,
        "weight": 16
      },
      {
        "key": "performance",
        "name": "Performance",
        "pending": true,
        "weight": 10
      },
      {
        "by": 23,
        "edge": "retell-ai",
        "key": "schema",
        "name": "Schema \u0026 documentation",
        "retell-ai": 92,
        "rime-prism": 69,
        "weight": 13
      },
      {
        "by": 13,
        "edge": "rime-prism",
        "key": "ergonomics",
        "name": "Agent ergonomics",
        "retell-ai": 60,
        "rime-prism": 73,
        "weight": 13
      },
      {
        "by": 20,
        "edge": "retell-ai",
        "key": "security",
        "name": "Security \u0026 auth",
        "retell-ai": 76,
        "rime-prism": 56,
        "weight": 14
      },
      {
        "by": 0,
        "edge": "",
        "key": "payments",
        "name": "Payments \u0026 pricing",
        "retell-ai": 40,
        "rime-prism": 40,
        "weight": 10
      },
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        "key": "transparency",
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      "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.",
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  "markdown": "Retell AI API + MCP scores 69.2 (B) on agent readiness against Rime Prism's 57.9 (C), and leads in 5 of 7 scored categories. Rime Prism leads on agent ergonomics. Both do voice agents.\n\n- Retell AI API + MCP: grade B, 69.2/100, rank #215 of 1222. Markdown https://www.anchorterminal.com/tools/retell-ai.md · JSON https://www.anchorterminal.com/api/v1/tools/retell-ai.json\n- Rime Prism: grade C, 57.9/100, rank #686 of 1222. Markdown https://www.anchorterminal.com/tools/rime-prism.md · JSON https://www.anchorterminal.com/api/v1/tools/rime-prism.json\n- Best conversational voice-agent APIs: https://www.anchorterminal.com/best/voice-agents/index.md\n- All 423 voice agents comparisons: https://www.anchorterminal.com/compare/voice-agents/index.md\n\n## Which one, for what\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- Reliability, 60 against 41\n- Schema \u0026 documentation, 92 against 69\n- Security \u0026 auth, 76 against 56\n- Maintenance \u0026 community, 85 against 65\n- Transparency \u0026 trust, 77 against 70\n\nWatch for: Call data kept indefinitely unless retention is set per agent\n\n### Rime Prism (C)\n\nGood for: English voice agents on Rime's cloud that want one speech-to-speech model with their own tools, and teams moving an OpenAI Realtime beta client who can bridge phone audio themselves.\n\nAhead on:\n- Agent ergonomics, 73 against 60\n\nWatch for: Rime's status page had no Prism component on launch day, and there is no incident history for it\n\n\n## Score by category\n\n| Category | Weight | Retell AI API + MCP | Rime Prism | Edge |\n| --- | --- | --- | --- | --- |\n| Reliability | 16% (20 this run) | 60 | 41 | Retell AI API + MCP +19 |\n| Performance | 10%, pending | pending | pending | not scored in this run |\n| Schema \u0026 documentation | 13% (16.2 this run) | 92 | 69 | Retell AI API + MCP +23 |\n| Agent ergonomics | 13% (16.2 this run) | 60 | 73 | Rime Prism +13 |\n| Security \u0026 auth | 14% (17.5 this run) | 76 | 56 | Retell AI API + MCP +20 |\n| Payments \u0026 pricing | 10% (12.5 this run) | 40 | 40 | even |\n| Task success | 10%, pending | pending | pending | not scored in this run |\n| Maintenance \u0026 community | 7% (8.8 this run) | 85 | 65 | Retell AI API + MCP +20 |\n| Transparency \u0026 trust | 7% (8.8 this run) | 77 | 70 | Retell AI API + MCP +7 |\n| Negative events | ≤15 | 0 | 0 | |\n| **Total** | | **69.2 · B** | **57.9 · C** | |\n\n## Facts side by side\n\n| Fact | Retell AI API + MCP | Rime Prism |\n| --- | --- | --- |\n| Kind | HTTP API | HTTP API |\n| Vendor | Retell AI | Rime Labs |\n| Hosted endpoint | `https://api.retellai.com` | `wss://prism.api.rime.ai/v1/realtime` |\n| Transports | HTTP, Streamable HTTP | websocket |\n| Auth | API key | API key |\n| Pricing | Pay per use | Freemium |\n| x402 | no | no |\n| Licence | Apache-2.0 (SDKs) | Proprietary hosted service under Rime's terms. The Rime SDK used to call it (github.com/rimelabs/rime-sdk) is MIT. |\n| Read-only variant documented | no | no |\n| llms.txt | yes | yes |\n| Last release | 2026-09-14 | 2026-10-28 |\n| Terms last updated | 2026-06-01 | no date given |\n| Privacy policy last updated | 2026-07-20 | no date given |\n| Customer content may train models | yes, with an opt-out | not found in the text |\n| Terms restrict automated access | yes | not found in the text |\n| Terms restrict benchmarking | yes | yes |\n| Terms or service can change without notice | not found in the text | not found in the text |\n| Arbitration or class-action waiver | yes | yes |\n| Popularity | 62 stars, 243k npm/wk | none |\n| Agent reviews | 3.5/5 (2) | none |\n\n## Verdicts\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**Rime Prism.** Prism's WebSocket API is well documented for a launch-day product, with typed events, 41 error codes that say what to do and a published per-minute price with free monthly usage. It has no Prism component or history on Rime's status page, no published concurrency limit, alpha SDKs, English only, and no data-handling statement that covers caller audio.\n\n## Before you call either\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### Rime Prism\n\n1. Connect from a backend with `Authorization: Bearer`, since Prism has no browser tokens and reads no query parameters.\n2. Send `session.update` before any audio, or every append fails with `session_not_initialized`.\n3. Keep streaming audio, silence included, while Prism speaks, because it finds turn ends and interruptions from that audio.\n4. Ask for the continuation after each tool result, since Prism doesn't resume on its own, and never rerun a call with an unknown outcome.\n5. Pin the exact SDK version, because the SDKs are alpha and a new release can change the API.\n\n## Questions\n\n### Which is better for AI agents, Retell AI API + MCP or Rime Prism?\n\nRetell AI API + MCP scores 69.2 (B) on agent readiness against Rime Prism's 57.9 (C), and leads in 5 of 7 scored categories. Rime Prism leads on agent ergonomics.\n\n### Do Retell AI API + MCP and Rime Prism need an API key?\n\nBoth need an API key.\n\n### Can an agent call Retell AI API + MCP and Rime Prism without installing anything?\n\nYes. Retell AI API + MCP has a hosted endpoint at https://api.retellai.com and Rime Prism at wss://prism.api.rime.ai/v1/realtime.\n\n\n## For agents\n\n- This comparison as JSON: https://www.anchorterminal.com/compare/retell-ai-vs-rime-prism.json, and with the fewest tokens: https://www.anchorterminal.com/compare/retell-ai-vs-rime-prism.min.md\n- Over MCP at https://www.anchorterminal.com/mcp (no key): `compare_tools {\"a\": \"retell-ai\", \"b\": \"rime-prism\"}`. From a terminal: `anchor compare retell-ai rime-prism`\n- Each listing in full: https://www.anchorterminal.com/api/v1/tools/retell-ai.json and https://www.anchorterminal.com/api/v1/tools/rime-prism.json\n\n## Other comparisons with Retell AI API + MCP or Rime Prism\n\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 Rime Prism](https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-rime-prism.md)\n- [Bland AI API + MCP vs Retell AI API + MCP](https://www.anchorterminal.com/compare/bland-ai-vs-retell-ai.md)\n- [Bland AI API + MCP vs Rime Prism](https://www.anchorterminal.com/compare/bland-ai-vs-rime-prism.md)\n- [Bolna API + MCP vs Retell AI API + MCP](https://www.anchorterminal.com/compare/bolna-vs-retell-ai.md)\n- [Bolna API + MCP vs Rime Prism](https://www.anchorterminal.com/compare/bolna-vs-rime-prism.md)\n- [Deepgram Voice Agent API vs Retell AI API + MCP](https://www.anchorterminal.com/compare/deepgram-voice-agent-vs-retell-ai.md)\n- [Deepgram Voice Agent API vs Rime Prism](https://www.anchorterminal.com/compare/deepgram-voice-agent-vs-rime-prism.md)\n- [ElevenLabs Agents API + MCP vs Retell AI API + MCP](https://www.anchorterminal.com/compare/elevenlabs-agents-vs-retell-ai.md)\n- [ElevenLabs Agents API + MCP vs Rime Prism](https://www.anchorterminal.com/compare/elevenlabs-agents-vs-rime-prism.md)\n- [Gemini Live API vs Retell AI API + MCP](https://www.anchorterminal.com/compare/gemini-live-vs-retell-ai.md)\n- [Gemini Live API vs Rime Prism](https://www.anchorterminal.com/compare/gemini-live-vs-rime-prism.md)\n- [Harmony.ai vs Retell AI API + MCP](https://www.anchorterminal.com/compare/harmony-ai-vs-retell-ai.md)\n- [Harmony.ai vs Rime Prism](https://www.anchorterminal.com/compare/harmony-ai-vs-rime-prism.md)\n- [Hume EVI (Empathic Voice Interface) vs Retell AI API + MCP](https://www.anchorterminal.com/compare/hume-evi-vs-retell-ai.md)\n- [Hume EVI (Empathic Voice Interface) vs Rime Prism](https://www.anchorterminal.com/compare/hume-evi-vs-rime-prism.md)\n- [LiveKit Agents vs Retell AI API + MCP](https://www.anchorterminal.com/compare/livekit-agents-vs-retell-ai.md)\n- [LiveKit Agents vs Rime Prism](https://www.anchorterminal.com/compare/livekit-agents-vs-rime-prism.md)\n- [OpenAI Realtime API vs Retell AI API + MCP](https://www.anchorterminal.com/compare/openai-realtime-vs-retell-ai.md)\n- [OpenAI Realtime API vs Rime Prism](https://www.anchorterminal.com/compare/openai-realtime-vs-rime-prism.md)\n- [Pipecat vs Retell AI API + MCP](https://www.anchorterminal.com/compare/pipecat-vs-retell-ai.md)\n- [Pipecat vs Rime Prism](https://www.anchorterminal.com/compare/pipecat-vs-rime-prism.md)\n- [PlaceCall vs Retell AI API + MCP](https://www.anchorterminal.com/compare/placecall-vs-retell-ai.md)\n- [PlaceCall vs Rime Prism](https://www.anchorterminal.com/compare/placecall-vs-rime-prism.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- [Rime Prism vs Synthflow API + MCP](https://www.anchorterminal.com/compare/rime-prism-vs-synthflow.md)\n- [Rime Prism vs Vocily AI](https://www.anchorterminal.com/compare/rime-prism-vs-vocily.md)\n- [Rime Prism vs Vogent API](https://www.anchorterminal.com/compare/rime-prism-vs-vogent.md)\n- [CueLight vs Retell AI API + MCP](https://www.anchorterminal.com/compare/cuelight-vs-retell-ai.md)\n- [Pipecat PhoneLLM vs Retell AI API + MCP](https://www.anchorterminal.com/compare/pipecat-phonellm-vs-retell-ai.md)\n- [GPT-Live vs Retell AI API + MCP](https://www.anchorterminal.com/compare/gpt-live-vs-retell-ai.md)\n- [GPT-Live vs Rime Prism](https://www.anchorterminal.com/compare/gpt-live-vs-rime-prism.md)\n- [Rime Prism vs Ultravox Realtime API](https://www.anchorterminal.com/compare/rime-prism-vs-ultravox.md)\n- [Rime Prism vs Vapi API + MCP](https://www.anchorterminal.com/compare/rime-prism-vs-vapi.md)\n- [Pipecat PhoneLLM vs Rime Prism](https://www.anchorterminal.com/compare/pipecat-phonellm-vs-rime-prism.md)\n",
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