fastmcp.server.providers.addressing

Deterministic tool hashing for backend-tool routing and per-tool resources.

Each FastMCPApp backend tool gets a deterministic hash computed from its app name + tool name. The hash serves two purposes:

1. Backend-tool routing. Tools with "app" in their visibility are callable via <hash>_<local_name>. The dispatcher parses the prefix, then walks providers recursively (same pattern as the old get_app_tool) to find a tool whose stored hash matches.

2. Per-tool Prefab renderer URIs. Each prefab tool gets a unique renderer resource at ui://prefab/tool/<hash>/renderer.html. list_resources and read_resource synthesize these on demand from the tool's meta.

The hash is computed at registration time from (app_name, tool_name) — both known at that moment — and stored in meta["fastmcp"]["_tool_hash"]. Deterministic across replicas (same code → same hash), no registry walk needed.

Functions

hash_tool ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/providers/addressing.py#L29" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

hash_tool(app_name: str, tool_name: str) -> str

Deterministic hex hash for a tool in an app.

Same inputs on every replica produce the same output.

hashed_backend_name ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/providers/addressing.py#L38" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

hashed_backend_name(app_name: str, tool_name: str) -> str

Format the universal name for a backend tool: <hash>_<local_name>.

parse_hashed_backend_name ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/providers/addressing.py#L43" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

parse_hashed_backend_name(name: str) -> tuple[str, str] | None

Parse <HASH_LENGTH hex>_<rest> → (hash, local_tool_name) or None.

hashed_resource_uri ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/providers/addressing.py#L55" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

hashed_resource_uri(app_name: str, tool_name: str) -> str

Per-tool Prefab renderer resource URI.

parse_hashed_resource_uri ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/providers/addressing.py#L60" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

parse_hashed_resource_uri(uri: str) -> str | None

Extract the hash from a Prefab renderer URI, or None.