Developer documentation
Three ways to work with First programmatically, and where to start with each.
Everything below uses the same credential: a personal access token you create yourself in First. You do not need us to provision anything for you.
In First, go to Profile, then Personal access tokens, and create one. Tokens begin fst_ and carry your own access, so a token can reach whatever you can reach and nothing more.
Send it as a bearer token on every request: Authorization: Bearer fst_...
GET /v1/organisations first to find the orgId you should be passing.A JSON API over the full role lifecycle: create, update, publish, pause, close, duplicate and archive roles; read applications; generate criteria; run reporting; and search for candidates.
Open the API reference for the full list of endpoints, with request and response shapes you can try in the browser. It is generated from the live API description, so it never drifts from the API itself.
First runs a Model Context Protocol server, which lets an AI assistant work in First directly rather than you writing the calls yourself. It exposes the same capabilities as the REST API as tools an assistant can use: reporting, the role lifecycle, sourcing candidates, talent market research, criteria generation and geocoding.
The endpoint is /mcp on the same host as the API. Clients that support bearer tokens can use the personal access token described above. Clients that sign in interactively, such as an AI assistant connecting on your behalf, use OAuth instead, and the applications you have approved are listed in First under Profile, then Connected applications.
Connect your agent with MCP covers connecting Claude or ChatGPT without writing any code. The MCP tool reference lists every tool the server exposes, generated from the live catalogue, along with which of them change data.
First already integrates with Greenhouse, Workable, Ashby, Teamtailor, Bullhorn, BambooHR, Pinpoint, Loxo and Eploy. For any of these, there is no engineering work at all: an administrator pastes an API key into First’s settings. Connect your ATS covers that.
If your ATS is off-the-shelf but not on that list, you do not need to build the integration yourself. Email support@first.cx and First will build it.
Building work is only needed in two situations: your ATS was built in house, so there is no published API for First to call, or you work for an ATS vendor and want your product to integrate with First. The custom ATS guide covers both.
Building something with First?
Tell us what you are trying to do. We would rather help you early than have you work around something we could change. Get in touch at support@first.cx