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fastmcp.client.auth.oauth

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Functions

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default_cache_dir 

default_cache_dir() -> Path

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check_if_auth_required 

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

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Classes

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ClientNotFoundError

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

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StoredToken

Token storage format with absolute expiry time.

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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:

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get_base_url 

get_base_url(url: str) -> str
Extract the base URL (scheme + host) from a URL.

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get_tokens 

get_tokens(self) -> OAuthToken | None
Load tokens from file storage.

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set_tokens 

set_tokens(self, tokens: OAuthToken) -> None
Save tokens to file storage.

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get_client_info 

get_client_info(self) -> OAuthClientInformationFull | None
Load client information from file storage.

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set_client_info 

set_client_info(self, client_info: OAuthClientInformationFull) -> None
Save client information to file storage.

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clear 

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.

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clear_all 

clear_all(cls, cache_dir: Path | None = None) -> None
Clear all cached data for all servers.

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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:

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redirect_handler 

redirect_handler(self, authorization_url: str) -> None
Open browser for authorization, with pre-flight check for invalid client.

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callback_handler 

callback_handler(self) -> tuple[str, str | None]
Handle OAuth callback and return (auth_code, state).

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async_auth_flow 

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.
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