# Add somebody to a project

`POST /api/v1/projects/{id}/members`

MCP tool: `add-project-member`

Invites somebody by email address, or by the `user_…` id of an existing account. They reach nothing in the project until they accept (`accept-invitation`). An address with no account gets one, never a refusal; the one refusal is a `user_…` id that names nobody. Idempotent. Admins only.

## Parameters

- `id` (path, required) — The project's `proj_…` id.

## Responses

- `200` — The member, and everyone else in the project
- `400` — The request body or query string does not match the operation's schema
- `401` — No Flow access token was presented, or it is not valid
- `403` — Authenticated, and not allowed — answered only where the caller already knows the resource exists. A project they are not a member of answers 404 instead.
- `404` — No such project, or none this caller is a member of