# API and MCP identity proxy

> Execute as a member of the same team through a trusted server and that member’s resource permissions.

Source: https://doc.fastgpt.io/en/openapi/identity-proxy

Identity proxy attributes an execution to a selected team member. The integration server authenticates the business user, resolves the member from a trusted mapping, and verifies the permitted delegation scope.

## Enablement requirements

* A team Owner can enable proxying on a team-level API key or MCP publication they manage. Creators can disable proxying on their own credentials or publications.
* The target must be an `active` member of the same team with application read permission and the relevant conversation permissions.
* API proxying requires a team-level API key with `authProxy` enabled. Legacy application-bound keys, login tokens, and shared-link credentials have their own access purposes.

## API request body

The conversation endpoint accepts `authProxy.username` or `authProxy.tmbId` in the request body:

```json
{
  "appId": "YOUR_APP_ID",
  "authProxy": { "username": "member@example.com" },
  "messages": [{ "role": "user", "content": "Summarize the travel policy." }],
  "stream": false
}
```

The username is the member's login username. When both `tmbId` and `username` are supplied in the API request body, `tmbId` takes precedence; if `tmbId` is invalid, the request fails directly and `username` is ignored. Omitting proxy fields uses the credential's member. Server-side permission checks determine access after membership or conversation ownership changes.

## MCP headers

MCP uses transport request headers:

```json
{
  "x-fastgpt-auth-proxy-username": "member@example.com"
}
```

Alternatively, use `x-fastgpt-auth-proxy-tmb-id`. Both headers must identify the same member when supplied together. SSE stores identity at connection time, so reconnect after changing identity. Streamable HTTP reads headers per request. See [MCP service publishing](/en/guide/build/publish/mcp_server) for complete connection examples.

## Verify and troubleshoot

Call as a member with read access and inspect conversation ownership. Then verify rejection using a test member lacking access. Check enablement, team, member status, identifier agreement, and resource permissions. An MCP tool list establishes metadata visibility; execution performs further permission checks.

The trusted server holds credentials and generates proxy fields. The user-facing client supplies business identity and the server authorizes its mapping. MCP identity proxying passes the member identifier through the `x-fastgpt-auth-proxy-username` or `x-fastgpt-auth-proxy-tmb-id` request header.