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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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OAuth

OAuth(mcp_url: str, scopes: str | list[str] | None = None, client_name: str = 'FastMCP Client', token_storage_cache_dir: Path | None = None, additional_client_metadata: dict[str, Any] | None = None) -> _MCPOAuthClientProvider

Create an OAuthClientProvider for an MCP server.

This is intended to be provided to the auth parameter of an httpx.AsyncClient (or appropriate FastMCP client/transport instance)

Args:

• mcp_url: Full URL to the MCP endpoint (e.g. “http://host/mcp/sse/”)
• scopes: OAuth scopes to request. Can be a
• client_name: Name for this client during registration
• token_storage_cache_dir: Directory for FileTokenStorage
• additional_client_metadata: Extra fields for OAuthClientMetadata

Returns:

• OAuthClientProvider

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Classes

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ServerOAuthMetadata

More flexible OAuth metadata model that accepts broader ranges of values than the restrictive MCP standard model.

This handles real-world OAuth servers like PayPal that may support additional methods not in the MCP specification.

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OAuthClientProvider

OAuth client provider with more flexible OAuth metadata discovery.

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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.

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_cache_key

get_cache_key(self) -> str

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

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clear

clear(self) -> None

Clear all cached data for this server.

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clear_all

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

Clear all cached data for all servers.