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## fastmcp.client.auth.oauth

### Functions

#### 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.

#### TokenStorageAdapter

**Methods:**

##### clear

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

##### get_tokens

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

##### set_tokens

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

##### get_token_expiry

```python
get_token_expiry(self) -> float | None
```

##### get_client_info

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

##### set_client_info

```python
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
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.