docs/python-sdk/fastmcp-server-auth-auth.mdx

---
title: auth
sidebarTitle: auth
---

# `fastmcp.server.auth.auth`

## Classes

### `AuthProvider` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/auth/auth.py#L25" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>


Base class for all FastMCP authentication providers.

This class provides a unified interface for all authentication providers,
whether they are simple token verifiers or full OAuth authorization servers.
All providers must be able to verify tokens and can optionally provide
custom authentication routes.


**Methods:**

#### `verify_token` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/auth/auth.py#L38" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
verify_token(self, token: str) -> AccessToken | None
```

Verify a bearer token and return access info if valid.

All auth providers must implement token verification.

**Args:**
- `token`: The token string to validate

**Returns:**
- AccessToken object if valid, None if invalid or expired


#### `customize_auth_routes` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/auth/auth.py#L51" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
customize_auth_routes(self, routes: list[Route]) -> list[Route]
```

Customize authentication routes after standard creation.

This method allows providers to modify or add to the standard OAuth routes.
The default implementation returns the routes unchanged.

**Args:**
- `routes`: List of standard routes (may be empty for token-only providers)

**Returns:**
- List of routes (potentially modified or extended)


### `TokenVerifier` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/auth/auth.py#L66" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>


Base class for token verifiers (Resource Servers).

This class provides token verification capability without OAuth server functionality.
Token verifiers typically don't provide authentication routes by default.


**Methods:**

#### `verify_token` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/auth/auth.py#L97" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
verify_token(self, token: str) -> AccessToken | None
```

Verify a bearer token and return access info if valid.


### `OAuthProvider` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/auth/auth.py#L102" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>


OAuth Authorization Server provider.

This class provides full OAuth server functionality including client registration,
authorization flows, token issuance, and token verification.


**Methods:**

#### `verify_token` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/auth/auth.py#L169" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
verify_token(self, token: str) -> AccessToken | None
```

Verify a bearer token and return access info if valid.

This method implements the TokenVerifier protocol by delegating
to our existing load_access_token method.

**Args:**
- `token`: The token string to validate

**Returns:**
- AccessToken object if valid, None if invalid or expired


#### `customize_auth_routes` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/auth/auth.py#L184" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
customize_auth_routes(self, routes: list[Route]) -> list[Route]
```

Customize OAuth authentication routes after standard creation.

This method allows providers to modify the standard OAuth routes
returned by create_auth_routes. The default implementation returns
the routes unchanged.

**Args:**
- `routes`: List of standard OAuth routes from create_auth_routes

**Returns:**
- List of routes (potentially modified)