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Windmill vs Zapier

Zapier scores higher on the AgentReady, 72/100 against 64/100. They differ on 6 of the 41 signals. Which ones decides whether an agent can adopt them without a person watching.

What each one is

Windmill. Windmill is a fast, open-source workflow engine and developer platform.

Zapier. Zapier gives teams one place to set guardrails, manage model access, and see everything — so everyone can build with AI confidently, on any model, without waiting for permission.

Where Windmill is ahead

Windmill passes fast time to first request and copyable quickstart, and Zapier does not. That is adopt, whether an agent can get a key and make its first successful call without a human in the loop.

Where Zapier is ahead

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

It also holds adopt: mcp integration available. Windmill misses it.

And on operate, structured, predictable output and retry behavior documented. Windmill misses those.

What neither does

Both fail openapi / spec quality, authentication documented, request examples provided, response examples provided, errors and status codes documented, no mandatory sales call, programmatic credential creation, machine-readable errors, idempotency support, rate-limit behavior predictable. 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. Zapier leads 100 to 87. Windmill misses mcp discoverable; Zapier misses nothing.

Understand. Both sit at 46/100 here. Windmill misses openapi / spec quality, authentication documented, request examples provided, response examples provided, errors and status codes documented; Zapier misses openapi / spec quality, authentication documented, request examples provided, response examples provided, errors and status codes documented.

Adopt. Zapier leads 70 to 67. Windmill misses no mandatory sales call, programmatic credential creation, mcp integration available; Zapier misses no mandatory sales call, programmatic credential creation, fast time to first request, copyable quickstart.

Operate is whether an agent can run against it in production and recover when a call fails. Zapier leads 72 to 56. Windmill misses structured, predictable output, machine-readable errors, retry behavior documented, idempotency support, rate-limit behavior predictable; Zapier misses machine-readable errors, idempotency support, rate-limit behavior predictable.

Pricing

Windmill does not publish a machine-readable starting price and has a free tier. Zapier does not publish one and has a free tier.

Signal by signal

Which to pick

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

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