fastmcp/docs/python-sdk/fastmcp-client-auth-oauth.mdx

---
title: oauth
sidebarTitle: oauth
---

# `fastmcp.client.auth.oauth`

## Functions

### `default_cache_dir` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/client/auth/oauth.py#L55" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
default_cache_dir() -> Path
```

### `check_if_auth_required` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/client/auth/oauth.py#L199" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
check_if_auth_required(mcp_url: str, httpx_kwargs: dict[str, Any] | None = None) -> bool
```


Check if the MCP endpoint requires authentication by making a test request.

**Returns:**
- True if auth appears to be required, False otherwise


## Classes

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


Raised when OAuth client credentials are not found on the server.


### `StoredToken` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/client/auth/oauth.py#L44" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>


Token storage format with absolute expiry time.


### `FileTokenStorage` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/client/auth/oauth.py#L59" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>


File-based token storage implementation for OAuth credentials and tokens.
Implements the mcp.client.auth.TokenStorage protocol.

Each instance is tied to a specific server URL for proper token isolation.


**Methods:**

#### `get_base_url` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/client/auth/oauth.py#L74" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
get_base_url(url: str) -> str
```

Extract the base URL (scheme + host) from a URL.


#### `get_cache_key` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/client/auth/oauth.py#L79" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
get_cache_key(self) -> str
```

Generate a safe filesystem key from the server's base URL.


#### `get_tokens` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/client/auth/oauth.py#L94" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
get_tokens(self) -> OAuthToken | None
```

Load tokens from file storage.


#### `set_tokens` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/client/auth/oauth.py#L126" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
set_tokens(self, tokens: OAuthToken) -> None
```

Save tokens to file storage.


#### `get_client_info` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/client/auth/oauth.py#L143" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
get_client_info(self) -> OAuthClientInformationFull | None
```

Load client information from file storage.


#### `set_client_info` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/client/auth/oauth.py#L171" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
set_client_info(self, client_info: OAuthClientInformationFull) -> None
```

Save client information to file storage.


#### `clear` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/client/auth/oauth.py#L177" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
clear(self) -> None
```

Clear all cached data for this server.


#### `clear_all` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/client/auth/oauth.py#L186" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
clear_all(cls, cache_dir: Path | None = None) -> None
```

Clear all cached data for all servers.


### `OAuth` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/client/auth/oauth.py#L229" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>


OAuth client provider for MCP servers with browser-based authentication.

This class provides OAuth authentication for FastMCP clients by opening
a browser for user authorization and running a local callback server.


**Methods:**

#### `redirect_handler` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/client/auth/oauth.py#L309" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
redirect_handler(self, authorization_url: str) -> None
```

Open browser for authorization, with pre-flight check for invalid client.


#### `callback_handler` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/client/auth/oauth.py#L330" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
callback_handler(self) -> tuple[str, str | None]
```

Handle OAuth callback and return (auth_code, state).


#### `async_auth_flow` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/client/auth/oauth.py#L363" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
async_auth_flow(self, request: httpx.Request) -> AsyncGenerator[httpx.Request, httpx.Response]
```

HTTPX auth flow with automatic retry on stale cached credentials.

If the OAuth flow fails due to invalid/stale client credentials,
clears the cache and retries once with fresh registration.