> ## Documentation Index
> Fetch the complete documentation index at: https://fastmcp-docs-v3-beta2-feature-tracking.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.
# oauth
# `fastmcp.client.auth.oauth`
## Functions
### `check_if_auth_required`
```python theme={null}
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.
### `TokenStorageAdapter`
**Methods:**
#### `clear`
```python theme={null}
clear(self) -> None
```
#### `get_tokens`
```python theme={null}
get_tokens(self) -> OAuthToken | None
```
#### `set_tokens`
```python theme={null}
set_tokens(self, tokens: OAuthToken) -> None
```
#### `get_client_info`
```python theme={null}
get_client_info(self) -> OAuthClientInformationFull | None
```
#### `set_client_info`
```python theme={null}
set_client_info(self, client_info: OAuthClientInformationFull) -> None
```
### `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 theme={null}
redirect_handler(self, authorization_url: str) -> None
```
Open browser for authorization, with pre-flight check for invalid client.
#### `callback_handler`
```python theme={null}
callback_handler(self) -> tuple[str, str | None]
```
Handle OAuth callback and return (auth\_code, state).
#### `async_auth_flow`
```python theme={null}
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.