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Retell vs Vapi

Vapi scores higher on the AgentReady, 78/100 against 47/100. They differ on 20 of the 41 signals. Which ones decides whether an agent can adopt them without a person watching.

What each one is

Retell. AI Voice Agent Platform for Automating Phone Calls.

Vapi. Vapi is the developer platform for building voice AI agents.

Where Retell is ahead

Retell passes mcp discoverable, and Vapi does not. That is discover, whether an agent can find the product at all without being told it exists.

It also holds adopt: official python sdk and mcp integration available. Vapi misses those.

Where Vapi is ahead

Vapi passes clear product positioning, and Retell does not. That is discover, whether an agent can find the product at all without being told it exists.

It also holds understand: openapi / spec quality, pricing understandable, request examples provided, response examples provided, errors and status codes documented and limits / constraints documented. Retell misses those.

And on adopt, self-service signup, programmatic credential creation, free trial or free allowance, fast time to first request and copyable quickstart. Retell misses those.

Finally, on operate, structured, predictable output, machine-readable errors, retry behavior documented, idempotency support and rate-limit behavior predictable. Retell misses those.

What neither does

Both fail authentication documented, no mandatory sales call, agent-compatible signup flow, cli available, agent compatibility verified. If your agent needs any of those, you will be building it yourself either way.

Score, pillar by pillar

The AgentReady splits into four pillars, scored separately, because a product can be easy to find and still impossible to adopt.

Discover. Both sit at 87/100 here. Retell misses clear product positioning; Vapi misses mcp discoverable.

Understand is whether an agent can read the docs and work out how the API behaves before calling it. Vapi leads 92 to 31. Retell misses openapi / spec quality, authentication documented, pricing understandable, request examples provided, response examples provided, errors and status codes documented, limits / constraints documented; Vapi misses authentication documented.

Adopt. Vapi leads 50 to 35. Retell misses self-service signup, no mandatory sales call, agent-compatible signup flow, programmatic credential creation, free trial or free allowance, fast time to first request, copyable quickstart, cli available; Vapi misses no mandatory sales call, agent-compatible signup flow, official python sdk, cli available, mcp integration available.

Operate. Vapi leads 82 to 35. Retell misses structured, predictable output, machine-readable errors, retry behavior documented, idempotency support, rate-limit behavior predictable, agent compatibility verified; Vapi misses agent compatibility verified.

Pricing

Retell does not publish a machine-readable starting price. Vapi starts at $0.05/min with no free tier.

Signal by signal

Which to pick

Vapi clears more of the signals an agent needs, so it is the safer default for unattended use. Full profiles: Retell and Vapi. Alternatives to each: Retell, Vapi.

An agent can fetch this as data: POST /v1/compare {"slugs": ["retellai", "vapi"]}