42min Developers MCP Server

42min developers

Public packaging and contracts for 42min, a meeting scheduling platform. This repository holds what you need to build on 42min or connect an AI agent to it. The product itself is closed source.

What is here

plugins/42min

The 42min plugin for Cursor. Connects the editor's agent to your 42min account over OAuth and exposes 35 scheduling tools. See its README.

Any MCP client can connect without this plugin, by pointing at https://api.42min.us/mcp. The server publishes OAuth protected-resource metadata, so a compliant client discovers everything else on its own.

openapi/42min.v1.yaml

The OpenAPI 3.1 description of the public REST API, for generating clients, importing into Postman or Bruno, and feeding to a coding agent.

It is hand-written, and checked against the running API by a contract test suite that exercises every documented endpoint and validates the live response, headers and error bodies against these schemas. That is how the first draft's seven mistakes were found, including two that would have broken every generated client on every booking write. A route-coverage check fails the build if an endpoint exists but is undocumented, or the reverse.

Those checks run in our private repository, because they boot the API against a real database and cannot run here. What CI in this repository enforces is that the file is a valid OpenAPI 3.1 document, so a malformed spec never reaches you.

If you find a place where this file and the API disagree, the file is probably wrong: please open an issue.

server.json

The official MCP Registry entry. Declares this as a remote server on streamable HTTP at https://api.42min.us/mcp, so registry-backed directories can list it without anyone hand-filling a form.

mcp/tools.json

The MCP contract, as a machine-readable snapshot: every tool with its JSON Schema for arguments, the scopes it needs, whether it writes, and the annotations a client uses to decide when to ask you before calling. Generated from the running tool registry, not hand-maintained, and gated by a test that fails when the two disagree.

Read it if you are building a client, or feed it to a coding agent. The table in the plugin README is the human summary of the same thing.

examples/webhook-receiver

A working receiver in about 120 lines with no dependencies, and ten tests for verify.js alone. Signature verification is where integrations break: the usual cause is verifying a re-serialized body rather than the raw bytes, which no amount of reading the docs makes obvious. Copy verify.js and move on.

Built on this API

• n8n community node (n8n-nodes-42min). Bookings, event types, slots and the current user, plus a trigger for every webhook event with signature verification built in. Runs inside your own n8n, so booking data goes from 42min to your server and nowhere else.

Authentication in one paragraph

Two mechanisms. OAuth 2.1 with PKCE for applications acting on behalf of a user, including Dynamic Client Registration, so a client can register itself without a support ticket. Personal access tokens for scripts acting as one person. Both carry scopes; the API refuses anything a token's scopes do not cover. Discovery documents live at /.well-known/oauth-authorization-server and /.well-known/oauth-protected-resource.

Full detail: Authentication.

Things worth knowing before you build

• Mutating booking calls accept Idempotency-Key. Retry with the same key. A new key creates a second booking.
• PATCH /v1/bookings/{uid} uses ETags. Read the ETag, send it back as If-Match, and a concurrent edit fails loudly instead of silently overwriting.
• There is no test environment yet. Write operations act on production: they send real email and create real calendar events. Test on event types you own, and clean up after yourself. (Our help pages use "sandbox" for something else, the per-credential isolation of webhook subscriptions.)
• Ignore unknown response fields. We add fields without notice; see CHANGELOG.md for the full versioning policy and the six-month deprecation guarantee.

Support

Open an issue for API bugs, specification errors, or plugin problems. Security reports go to plus@42min.us, not to the issue tracker: see SECURITY.md.

License

MIT. See LICENSE.