Initialize a Stdio transport. Args: command: The command to run (e.g., "python", "node", "uvx") args: The ar

Return the exact decoded byte-length of a base64 string without decoding it.

An SDK MCPServer whose tools/list carries a positive ttlMs hint at 2026.

Derive a human-friendly name from a server spec.

Whether a session record exists for this `(principal, session_id)`. True only once `create_session` has written the creation marker. A raw

Fetch the latest version from PyPI. Args: include_prereleases: If True, include pre-release versions (alpha, beta, rc). Returns:

Return a stable, hashed identifier for the current access token. Cache entries are partitioned by access token so that responses filtered by

Load visibility rule dicts from session state.

Generate a deterministic hash for schema caching. Handles non-JSON-native types (datetime, date, bool keys) that can appear in schemas loaded

Hash a token for secure storage lookup. Uses SHA-256 to create a one-way hash. The original token cannot be recovered from the hash, providin

Read the session's full stored dict, or `None` when the key is unset.

Log error with appropriate detail level.

Create an UpstreamTokenSet with optional id_token.

Normalize editor-specific server config fields to MCPConfig format. Handles two known differences: - Claude Code uses ``type`` where MCPConfi

Parse environment variable string in format KEY=VALUE.

Prepare scopes for Azure authorization code exchange. Azure requires scopes during token exchange (AADSTS28003 error if missing). Azu

Set up a proxy JWT pointing at an expired upstream token. Returns the proxy JWT (access token) that can be passed to load_access_toke

Register client and start auth; returns (txn_id, consent_url).

Text from CallToolResult.content blocks (TextContent).

Apply runtime settings like environment variables and working directory. Args: config_path: Path to config file for resolving rel

Run a tool sync and as a task; assert the inlined results are identical.

HTTPX auth flow with automatic retry on stale cached credentials. If the OAuth flow fails due to invalid/stale client credentials, cl

Server whose cart tools inject a per-user `session: UserSession`.

Build regex pattern for URI template, handling RFC 6570 syntax. Supports: - `{var}` - simple path parameter - `{var*}` - wildcard path pa

Call a sync function in a threadpool to avoid blocking the event loop. Uses anyio.to_thread.run_sync which properly propagates contextvars, m

Call multiple tools registered on this MCP server in a single request. Each call can be for a different tool and can include differe

Check whether the connected client supports a given MCP extension. Inspects the ``extensions`` capability on ``ClientCapabilities`` sent by the

Create an OAuth callback server. Args: port: The port to run the server on callback_path: The path to listen for OAuth redir

The authenticated principal for the current request as a compact JSON string. Returns the `(client_id, issuer, subject)` triple encoded as compac

Decode JWT payload without signature verification. Use only for tokens received directly from trusted sources (e.g., IdP token endpoints). A

Disable components matching criteria for this session only. Session rules override global transforms. Rules accumulate - each call ad

Find a fastmcp.json file in the specified directory. Args: start_path: Directory to look in (defaults to current directory)

Get all recorded calls for a specific method or hook. Args: method: The method to filter by (e.g. "tools/list")

Get client information by ID. This is generally the random ID provided to the DCR client during registration, not the upstream client ID.

Get a resource by URI, filtering disabled resources. Overrides Provider.get_resource() to add visibility filtering after all transfor

Get the manifest for a specific skill. Args: client: Connected FastMCP client skill_name: Name of the skill Returns:

Get the current task context if running inside a background task worker. This function extracts task information from the Docket execution contex

Get the FastMCP tracer for creating spans. Instrumentation is on by default. FastMCP uses only the OpenTelemetry API, so span creation is a n

Install FastMCP server in Cursor. Args: file: Path to the server file server_object: Optional server object name (for :object suf

Check if cls is a subclass of base, even if cls is a type variable.

Issue a minimal FastMCP refresh token. FastMCP refresh tokens are reference tokens containing only the minimal claims needed for vali

Retrieve all tools available on the server. This method automatically fetches all pages if the server paginates results, returning th

Whether FastMCP should create its own spans right now.

Create a new client instance with the same configuration but fresh session state. This creates a new client with the same transport, handlers

Coerce a handler's return value into a wire ``Completion``. A returned ``str`` is rejected: it is almost always a mistake (the value would it

Prepare environment and source for execution. When output_dir is provided, creates a persistent uv project. When output_dir is None,

Raise ImportError with install instructions if docket not available. Args: feature: Description of what requires docket (e.g., "`task=Tru

Require scopes when the accessed component has a specific tag.

Serialize a resolved transport to a Python expression string. Returns ``(expression, extra_imports)`` where *extra_imports* is a set of impor

Names of a function's parameters annotated with `SessionId`. Scans resolved type hints for `Annotated[str, _SessionIdMarker()]` metadata. Ret

The single storage key holding a session's state dict. Keyed by `(principal, session_id)`: the principal is the isolation wall, the id organi

Translate a FastMCP exception into a wire-format ``MCPError``. Central mapping from FastMCP's public exception types to the JSON-RPC error co

Verify a bearer token and return access info if valid. This method implements the TokenVerifier protocol by delegating to ou

Fill in missing boolean fields with their model defaults. HTML checkboxes omit the field entirely when unchecked, so the submitted data dict

Shell-split a command string into a ``StdioTransport``.

Build a minimal ~/.claude.json structure.

Collect successful list results, logging any exceptions. Emits a warning when the same MCP identity is returned by more than one prov

Construct a provider with mocked discovery, returning the timeout used.

Convert MCP tool_choice to Anthropic format. Returns None for "none" mode, signaling that tools should be omitted from the request en

Write the initial record so the session exists (called by `create_session`).

Helper to create a test RemoteAuthProvider with StaticTokenVerifier.

Disconnect from session using reference counting. This method implements proper cleanup for reentrant context managers: - De

Lazily register tools and resources on first access.

Extract scopes from JWT claims. Supports both 'scope' and 'scp' claims. Checks the `scope` claim first (standard OAuth2 clai

Extract an AzureProvider from an auth provider, unwrapping MultiAuth if needed.

Build the Starlette dev server application.

Create a CallTool resolver that addresses peer tools by identity. ``app_name`` is the FastMCPApp's name, known at serialization time from the

Parse an mcp_types.CallToolResult into our CallToolResult dataclass. Args: name: Tool name (for schema lookup) result: Raw MCP pr

Report an unreachable backend the same way however the failure arrived. Depending on where the dead connection is noticed, the proxy sees either

Resolves a reference to its target definition.

Escape rich markup and encode control chars for terminal-safe output.

Walk up from *start_dir* looking for ``.cursor/mcp.json``.

Scan Gemini CLI settings for MCP servers. Checks both user-level ``~/.gemini/settings.json`` and project-level ``.gemini/settings.json``.