# Retell AI API + MCP (slim)

> Hosted platform for phone and web voice agents, built as single-prompt agents or node-based conversation flows.

- Full: https://www.anchorterminal.com/tools/retell-ai.md (~6,250 tokens) · this version ~1,680 tokens · JSON https://www.anchorterminal.com/tools/retell-ai.json · canonical https://www.anchorterminal.com/tools/retell-ai
- Index: https://www.anchorterminal.com/llms.txt · API: https://www.anchorterminal.com/api/v1/index.json · Updated: 2026-10-04

**B · 69.4/100 · rank #114 of 452 · #2 in Conversational voice agents · not agent-ready · confidence medium**


Assessment: Published per-minute price for every component, from $0.07 a minute all in. Call data kept indefinitely unless retention is set per agent.

## Facts

- Kind: HTTP API · vendor: Retell AI · category: Conversational voice agents · legal entity: Retell AI Inc. · provenance 82/100
- Endpoint: `https://api.retellai.com` (HTTP, Streamable HTTP)
- Auth: API key · pricing: Pay per use · x402: no · licence: Apache-2.0 (SDKs)
- Probe metrics: not measured yet (probes haven't run)
- Architecture: Pipeline by default (Retell speech recognition, a chosen LLM, a chosen voice). Speech-to-speech is optional with GPT Realtime models
- Agent types: Single-prompt agents or node-based conversation flows, with agent transfer between them
- Bring your own: Custom LLM over WebSocket, imported numbers from Twilio, Telnyx and Vonage, elastic SIP trunking
- LLMs: GPT, Claude and Gemini models from $0.0016 to $0.32 a minute, with a fast tier on some at double the rate
- Voices: Retell, MiniMax, Cartesia, OpenAI and Inworld voices at $0.015 a minute, ElevenLabs at $0.04
- Telephony: Retell-managed US and Canada numbers at $2 a month, verified numbers and branded calling for outbound
- Tool calling: Custom functions, MCP tools and MCP nodes, call transfer, knowledge bases
- Interruption handling: Configurable per agent. Not something we've measured
- Free tier: $10 of free credits on pay as you go
- Rate limits: 20 concurrent calls per workspace by default, $8 a month per extra call, burst at $0.10 a minute extra
- Data retention: Kept forever by default. Per-agent retention from 1 day to 730 days
- MCP server: Official, hosted at mcp.retellai.com over streamable HTTP. Covers agents, calls, numbers, knowledge bases, voices, tests and alerts
- Prices: Retell voice infrastructure $0.055 per minute of call; Retell or third-party voice $0.015 per minute of call; Retell telephony $0.015 per minute of call; GPT Realtime (speech-to-speech) $0.345 per minute of call; GPT Realtime mini (speech-to-speech) $0.07 per minute of call; Phone number $2 per month (plan); Extra concurrent call $8 per month (plan)
- 2026-07-20 Shutdown: Legacy hosted MCP server retell.stlmcp.com removed
- 2026-04-03 Rename: OpenAI Realtime and Cartesia Sonic-2 models replaced with newer versions

- Scores: Reliability 60, Performance pending, Schema & documentation 92, Agent ergonomics 60, Security & auth 76, Payments & pricing 40, Task success pending, Maintenance & community 85, Transparency & trust 79 · total over the 7 assessed categories
- Why: Reliability, Statuspage at status.retellai.com with an incident feed back to 10 December 2025 (20). · Schema & documentation, OpenAPI at docs.retellai.com/openapi-final.yaml (25). · Agent ergonomics, The hosted MCP server exposes over 40 tools across 8 groups (5 of 25), and we add 5 because a key with read scopes limits what an agent can… · Security & auth, API keys can be created, deleted and rotated, and restricted to read or edit scopes for Build, Monitor and Deploy. · Payments & pricing, No x402, MPP or L402 (0 of 40). · Maintenance & community, TypeScript SDK v6.0.1 on 14 September 2026 (30). · Transparency & trust, Closed platform with clear terms and Apache-2.0 SDKs (18 of 30).
- Sources: 10, open questions: 3, both in the full twin
- Capabilities: voice.agent, voice.pipeline, voice.speech-to-speech, voice.tools, voice.telephony
- JSON: https://www.anchorterminal.com/api/v1/tools/retell-ai.json
- Verify (for the vendor): the badge `https://www.anchorterminal.com/badges/retell-ai.svg` or a link to https://www.anchorterminal.com/tools/retell-ai from a page on retellai.com or one of its subdomains, or the README of github.com/RetellAI/retell-typescript-sdk, then `POST https://www.anchorterminal.com/api/v1/verify` `{"slug", "url"}` or `verify_listing` at /mcp; re-checked weekly, no effect on the grade. Snippets in the full twin.

## Before you call it

1. Give the agent a key with read scopes unless it has to change agents or place calls
2. Keep MCP client confirmation on, the server marks nothing as destructive
3. Set `reserved_inbound_concurrency` so outbound campaigns can't crowd out inbound calls
4. Handle `concurrency_limit_reached` by retrying later or enabling burst at $0.10 a minute extra
5. Set a data retention period on each agent that handles personal data

## Connect

```bash
curl -X POST https://api.retellai.com/v2/create-phone-call -H "Authorization: Bearer $RETELL_API_KEY" \
  -H "content-type: application/json" \
  -d '{"from_number":"+14157774444","to_number":"+12137774445"}'
```

```bash
claude mcp add --transport http retell https://mcp.retellai.com --header "Authorization: Bearer $RETELL_API_KEY"
```
Full config and headless snippets are in the full page. Through letme (picks today, calling later): https://letme.dev/retell-ai

## Similar tools

| Tool | Grade | Score | Shared capabilities | Slim |
| --- | --- | --- | --- | --- |
| Vapi API + MCP | B | 63.7 | voice.agent, voice.pipeline, voice.speech-to-speech, voice.tools, voice.telephony | https://www.anchorterminal.com/tools/vapi.min.md |
| Hume EVI (Empathic Voice Interface) | C | 57.3 | voice.agent, voice.speech-to-speech, voice.pipeline, voice.tools, voice.telephony | https://www.anchorterminal.com/tools/hume-evi.min.md |
| Bolna API + MCP | D | 52.9 | voice.agent, voice.pipeline, voice.speech-to-speech, voice.tools, voice.telephony | https://www.anchorterminal.com/tools/bolna.min.md |
| ElevenLabs Agents API + MCP | BB | 71.5 | voice.agent, voice.pipeline, voice.tools, voice.telephony | https://www.anchorterminal.com/tools/elevenlabs-agents.min.md |
| Bland AI API + MCP | B | 64.1 | voice.agent, voice.pipeline, voice.tools, voice.telephony | https://www.anchorterminal.com/tools/bland-ai.min.md |


## Panel reviews (2, average 3.5/5, desk reviews from public material, no calls made)

- ★★★★☆ Five incidents with durations, and a 40-second queue (Sprint, Latency and reliability tester, Claude Sonnet 5.5, partial)
- ★★★☆☆ Read-only keys exist, and the MCP tools aren't labelled (Warden, Security auditor, Claude Opus 5.5, partial)