The API that isn’t
built yet, answering.
Upload an OpenAPI document and every endpoint in it goes live at a URL, answering with data that fits the schema: right types, right enums, right formats, believable names and dates. Seed it to make it repeatable, steer the status per call, pin an answer when you need one.
Free. Sign in with Google. OpenAPI 3.0, 3.1 and Swagger 2.0.
From a YAML file to a running API in one upload.
- 01
Upload the spec
Paste it, drop the file or point at a URL. mockit parses it, lifts Swagger 2.0 to OpenAPI 3, and indexes every method and path. Refs are resolved on the fly, cycles included.
- 02
Get a base URL
Each spec gets a short unguessable id. The base URL plus the path in your spec is the mock endpoint. Point a frontend, a test suite or a teammate at it. No keys, no CORS trouble.
- 03
Call it
Responses are generated from the response schema: enums, formats, ranges, patterns, required fields, oneOf and discriminators. Field names shape the data, so an email looks like an email.
- 04
Steer it
Ask for a 404 with one header, replay a body with a seed, add latency, or pin an endpoint to a fixed answer. Turn on request validation and it rejects calls that break the contract.
Built for the week before the backend exists.
Seeds, not randomness
Send x-mockit-seed: 42 and the same body comes back every time. Set a workspace seed and every endpoint becomes stable, so tests can assert on it.
Steer per call
?_status=404 or Prefer: code=404 picks that response from the spec. ?_delay=800 adds latency. Nothing to configure first.
Validation, if you want it
Turn it on and the mock rejects calls that break the contract: missing required fields, wrong types, bad enums, out-of-range numbers, with a list of what is wrong.
Examples win
An example in the spec is returned as written. Everything else is generated, and readOnly / writeOnly fields land on the right side of the wire.
Every call logged
The request log shows what hit the mock, which operation answered, with what status and how fast. Handy when the frontend swears it called the right thing.
Pinned answers
Override an endpoint with a fixed status, body, headers or delay. Reproduce that one production failure on demand; clear it to go back to generating.
Workspaces
Specs live in workspaces. Invite editors who upload and tune, or viewers who only read and call. Invites are links that expire.
An MCP endpoint
Your agent lists specs, reads endpoint schemas, generates or calls mock responses and pins overrides, signed in with the same account over OAuth.
Your agent can read the spec and call the mock.
One streamable-HTTP endpoint, Clerk OAuth on first connect. Ten tools: list workspaces and specs, list and inspect endpoints, generate or call a mock response, read the request log, upload a spec, set and clear overrides. Same roles as the dashboard.
# Claude Code
claude mcp add --transport http mockit \
https://mockit.unhingged.com/api/mcp
# then, in a session
> list the endpoints of the payments spec and
pin POST /charges to a 402 with a decline body