fastmcp.server.providers.proxy

ProxyProvider for proxying to remote MCP servers.

This module provides the ProxyProvider class that proxies components from a remote MCP server via a client factory. It also provides proxy component classes that forward execution to remote servers.

Functions

default_proxy_roots_handler ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/providers/proxy.py#L852" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

default_proxy_roots_handler(context: RequestContext[ClientSession, LifespanContextT]) -> RootsList

Forward list roots request from remote server to proxy's connected clients.

default_proxy_sampling_handler ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/providers/proxy.py#L860" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

default_proxy_sampling_handler(messages: list[mcp.types.SamplingMessage], params: mcp.types.CreateMessageRequestParams, context: RequestContext[ClientSession, LifespanContextT]) -> mcp.types.CreateMessageResult

Forward sampling request from remote server to proxy's connected clients.

default_proxy_elicitation_handler ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/providers/proxy.py#L883" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

default_proxy_elicitation_handler(message: str, response_type: type, params: mcp.types.ElicitRequestParams, context: RequestContext[ClientSession, LifespanContextT]) -> ElicitResult

Forward elicitation request from remote server to proxy's connected clients.

default_proxy_log_handler ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/providers/proxy.py#L905" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

default_proxy_log_handler(message: LogMessage) -> None

Forward log notification from remote server to proxy's connected clients.

default_proxy_progress_handler ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/providers/proxy.py#L913" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

default_proxy_progress_handler(progress: float, total: float | None, message: str | None) -> None

Forward progress notification from remote server to proxy's connected clients.

Classes

ProxyTool ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/providers/proxy.py#L69" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

A Tool that represents and executes a tool on a remote server.

Methods:

model_copy ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/providers/proxy.py#L86" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

model_copy(self, **kwargs: Any) -> ProxyTool

Override to preserve _backend_name when name changes.

from_mcp_tool ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/providers/proxy.py#L96" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

from_mcp_tool(cls, client_factory: ClientFactoryT, mcp_tool: mcp.types.Tool) -> ProxyTool

Factory method to create a ProxyTool from a raw MCP tool schema.

run ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/providers/proxy.py#L114" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

run(self, arguments: dict[str, Any], context: Context | None = None) -> ToolResult

Executes the tool by making a call through the client.

get_span_attributes ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/providers/proxy.py#L169" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

get_span_attributes(self) -> dict[str, Any]

ProxyResource ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/providers/proxy.py#L176" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

A Resource that represents and reads a resource from a remote server.

Methods:

model_copy ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/providers/proxy.py#L201" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

model_copy(self, **kwargs: Any) -> ProxyResource

Override to preserve _backend_uri when uri changes.

from_mcp_resource ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/providers/proxy.py#L211" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

from_mcp_resource(cls, client_factory: ClientFactoryT, mcp_resource: mcp.types.Resource) -> ProxyResource

Factory method to create a ProxyResource from a raw MCP resource schema.

read ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/providers/proxy.py#L231" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

read(self) -> ResourceResult

Read the resource content from the remote server.

get_span_attributes ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/providers/proxy.py#L276" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

get_span_attributes(self) -> dict[str, Any]

ProxyTemplate ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/providers/proxy.py#L283" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

A ResourceTemplate that represents and creates resources from a remote server template.

Methods:

model_copy ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/providers/proxy.py#L300" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

model_copy(self, **kwargs: Any) -> ProxyTemplate

Override to preserve _backend_uri_template when uri_template changes.

from_mcp_template ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/providers/proxy.py#L310" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

from_mcp_template(cls, client_factory: ClientFactoryT, mcp_template: mcp.types.ResourceTemplate) -> ProxyTemplate

Factory method to create a ProxyTemplate from a raw MCP template schema.

create_resource ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/providers/proxy.py#L329" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

create_resource(self, uri: str, params: dict[str, Any], context: Context | None = None) -> ProxyResource

Create a resource from the template by calling the remote server.

get_span_attributes ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/providers/proxy.py#L391" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

get_span_attributes(self) -> dict[str, Any]

ProxyPrompt ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/providers/proxy.py#L398" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

A Prompt that represents and renders a prompt from a remote server.

Methods:

model_copy ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/providers/proxy.py#L415" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

model_copy(self, **kwargs: Any) -> ProxyPrompt

Override to preserve _backend_name when name changes.

from_mcp_prompt ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/providers/proxy.py#L425" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

from_mcp_prompt(cls, client_factory: ClientFactoryT, mcp_prompt: mcp.types.Prompt) -> ProxyPrompt

Factory method to create a ProxyPrompt from a raw MCP prompt schema.

render ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/providers/proxy.py#L449" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

render(self, arguments: dict[str, Any]) -> PromptResult

Render the prompt by making a call through the client.

get_span_attributes ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/providers/proxy.py#L471" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

get_span_attributes(self) -> dict[str, Any]

ProxyProvider ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/providers/proxy.py#L499" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

Provider that proxies to a remote MCP server via a client factory.

This provider fetches components from a remote server and returns Proxy* component instances that forward execution to the remote server.

All components returned by this provider have task_config.mode="forbidden" because tasks cannot be executed through a proxy.

Component lists (tools, resources, templates, prompts) are cached so that individual lookups (e.g. during call_tool) can resolve from the cache instead of opening a new backend connection. The cache stores the backend's raw component metadata and is shared across all sessions; per-session visibility and auth filtering are applied after cache lookup by the server layer. The cache is refreshed whenever a list_* call is made, and entries expire after cache_ttl seconds (default 300). Set cache_ttl=0 to disable caching. Disabling is recommended for backends whose component lists change dynamically.

Methods:

get_tasks ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/providers/proxy.py#L715" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

get_tasks(self) -> Sequence[FastMCPComponent]

Return empty list since proxy components don't support tasks.

Override the base implementation to avoid calling list_tools() during server lifespan initialization, which would open the client before any context is set. All Proxy* components have task_config.mode="forbidden".

FastMCPProxy ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/providers/proxy.py#L805" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

A FastMCP server that acts as a proxy to a remote MCP-compliant server.

This is a convenience wrapper that creates a FastMCP server with a ProxyProvider. For more control, use FastMCP with add_provider(ProxyProvider(...)).

ProxyClient ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/providers/proxy.py#L977" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

A proxy client that forwards advanced interactions between a remote MCP server and the proxy's connected clients.

Supports forwarding roots, sampling, elicitation, logging, and progress.

StatefulProxyClient ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/providers/proxy.py#L1019" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

A proxy client that provides a stateful client factory for the proxy server.

The stateful proxy client bound its copy to the server session. And it will be disconnected when the session is exited.

This is useful to proxy a stateful mcp server such as the Playwright MCP server. Note that it is essential to ensure that the proxy server itself is also stateful.

Because session reuse means the receive-loop task inherits a stale request_ctx ContextVar snapshot, the default proxy handlers are replaced with versions that restore the ContextVar before forwarding. ProxyTool.run stashes the current RequestContext in _proxy_rc_ref before each backend call, and the handlers consult it to detect (and correct) staleness.

Methods:

clear ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/providers/proxy.py#L1070" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

clear(self)

Clear all cached clients and force disconnect them.

new_stateful ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/providers/proxy.py#L1076" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

new_stateful(self) -> Client[ClientTransportT]

Create a new stateful proxy client instance with the same configuration.

Use this method as the client factory for stateful proxy server.