---
title: oauth
sidebarTitle: oauth
---
# `fastmcp.client.auth.oauth`
## Functions
### `default_cache_dir`
```python
default_cache_dir() -> Path
```
### `check_if_auth_required`
```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`
Raised when OAuth client credentials are not found on the server.
### `StoredToken`
Token storage format with absolute expiry time.
### `FileTokenStorage`
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.
Uses JSONFileStorage internally for consistent file handling.
**Methods:**
#### `get_base_url`
```python
get_base_url(url: str) -> str
```
Extract the base URL (scheme + host) from a URL.
#### `get_tokens`
```python
get_tokens(self) -> OAuthToken | None
```
Load tokens from file storage.
#### `set_tokens`
```python
set_tokens(self, tokens: OAuthToken) -> None
```
Save tokens to file storage.
#### `get_client_info`
```python
get_client_info(self) -> OAuthClientInformationFull | None
```
Load client information from file storage.
#### `set_client_info`
```python
set_client_info(self, client_info: OAuthClientInformationFull) -> None
```
Save client information to file storage.
#### `clear`
```python
clear(self) -> None
```
Clear all cached data for this server.
Note: This is a synchronous method for backward compatibility.
Uses direct file operations instead of async storage methods.
#### `clear_all`
```python
clear_all(cls, cache_dir: Path | None = None) -> None
```
Clear all cached data for all servers.
### `OAuth`
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`
```python
redirect_handler(self, authorization_url: str) -> None
```
Open browser for authorization, with pre-flight check for invalid client.
#### `callback_handler`
```python
callback_handler(self) -> tuple[str, str | None]
```
Handle OAuth callback and return (auth_code, state).
#### `async_auth_flow`
```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.