Retell AI is a platform to build, test, and deploy AI voice agents for phone calls. Its conversational voice API orchestrates LLM responses, telephony, speech, and call analysis so developers can place and receive natural-sounding automated calls, with a real-time WebSocket for bringing your own custom LLM and streaming call audio.
APIs.json: https://raw.githubusercontent.com/api-evangelist/retell/refs/heads/main/apis.yml
- AI
- Voice
- Voice Agents
- Conversational AI
- Telephony
- Created: 2026-07-01
- Modified: 2026-07-01
Create, retrieve, list, update, and delete voice agents that pair a response engine (Retell LLM, custom LLM, or conversation flow) with a voice and call-behavior settings.
- Human URL: https://docs.retellai.com/api-references/create-agent
- Base URL:
https://api.retellai.com
- Agents
- Voice Agents
- Configuration
- Documentation
- API Reference
- OpenAPI — OpenAPI Specification
- Postman Collection — Postman Collection 2.1
- Open Collection — Open Collection 1.0
Manage the Retell-hosted LLM response engine — general prompt, model, temperature, tools, multi-state flows, begin message, and knowledge base references that drive agent conversations.
- Human URL: https://docs.retellai.com/api-references/create-retell-llm
- Base URL:
https://api.retellai.com
- LLM
- Orchestration
- Prompt
- Documentation
- API Reference
- OpenAPI — OpenAPI Specification
- Postman Collection — Postman Collection 2.1
- Open Collection — Open Collection 1.0
Manage node/edge conversation flows for visually structured, deterministic agent conversations as an alternative response engine to the Retell LLM.
- Human URL: https://docs.retellai.com/api-references/create-conversation-flow
- Base URL:
https://api.retellai.com
- Conversation Flow
- Node Graph
- Deterministic
- Documentation
- API Reference
- OpenAPI — OpenAPI Specification
- Postman Collection — Postman Collection 2.1
- Open Collection — Open Collection 1.0
Place outbound PSTN calls (POST /v2/create-phone-call) and retrieve or list completed calls with transcript, recording URL, call analysis, and cost breakdown.
- Human URL: https://docs.retellai.com/api-references/create-phone-call
- Base URL:
https://api.retellai.com
- Phone Call
- Outbound
- Telephony
- Documentation
- API Reference
- OpenAPI — OpenAPI Specification
- Postman Collection — Postman Collection 2.1
- Open Collection — Open Collection 1.0
Register browser-based (WebRTC) calls (POST /v2/create-web-call) and receive an access_token to hand to the Retell Web Client SDK for real-time in-browser voice conversations.
- Human URL: https://docs.retellai.com/api-references/create-web-call
- Base URL:
https://api.retellai.com
- Web Call
- WebRTC
- Browser
- Documentation
- API Reference
- OpenAPI — OpenAPI Specification
- AsyncAPI — AsyncAPI Specification
- Postman Collection — Postman Collection 2.1
- Open Collection — Open Collection 1.0
Buy Retell-managed numbers or import your own via SIP trunk, and bind inbound and outbound agents to each number for automated call handling.
- Human URL: https://docs.retellai.com/api-references/create-phone-number
- Base URL:
https://api.retellai.com
- Phone Numbers
- Provisioning
- SIP
- Documentation
- API Reference
- OpenAPI — OpenAPI Specification
- Postman Collection — Postman Collection 2.1
- Open Collection — Open Collection 1.0
List and retrieve the catalog of available voices across TTS providers (ElevenLabs, OpenAI, PlayHT, Cartesia, Deepgram) with accent, gender, age, and preview audio.
- Human URL: https://docs.retellai.com/api-references/list-voices
- Base URL:
https://api.retellai.com
- Voices
- TTS
- Speech
- Documentation
- API Reference
- OpenAPI — OpenAPI Specification
- Postman Collection — Postman Collection 2.1
- Open Collection — Open Collection 1.0
Create knowledge bases from texts, files, and URLs, manage their sources, and reference them from a Retell LLM or conversation flow for retrieval-augmented answers during calls.
- Human URL: https://docs.retellai.com/api-references/create-knowledge-base
- Base URL:
https://api.retellai.com
- Knowledge Base
- RAG
- Retrieval
- Documentation
- API Reference
- OpenAPI — OpenAPI Specification
- Postman Collection — Postman Collection 2.1
- Open Collection — Open Collection 1.0
Queue outbound calling campaigns to many recipients from a single from_number with per-task dynamic variables, subject to available call concurrency.
- Human URL: https://docs.retellai.com/api-references/create-batch-call
- Base URL:
https://api.retellai.com
- Batch Call
- Campaigns
- Outbound
- Documentation
- API Reference
- OpenAPI — OpenAPI Specification
- Postman Collection — Postman Collection 2.1
- Open Collection — Open Collection 1.0
Read the organization's current and maximum simultaneous-call concurrency (GET /get-concurrency) — the primary capacity and throttling lever for outbound and batch calling.
- Human URL: https://docs.retellai.com/api-references/get-concurrency
- Base URL:
https://api.retellai.com
- Concurrency
- Rate Limiting
- Capacity
- API Reference
- OpenAPI — OpenAPI Specification
- Rate Limits
- Postman Collection — Postman Collection 2.1
- Open Collection — Open Collection 1.0
FN: Kin Lane Email: kin@apievangelist.com