Merge pull request jlowin#301 from jlowin/client

Add low-level methods to client

Author: jlowin

docs/clients/client.mdx

@@ -149,6 +149,34 @@ The `Client` provides methods corresponding to standard MCP requests:
 *   **`list_prompts()`**: Retrieves available prompt templates.
 *   **`get_prompt(name: str, arguments: dict[str, Any] | None = None)`**: Retrieves a rendered prompt message list.
 
+### Raw MCP Protocol Objects
+
+The FastMCP client attempts to provide a "friendly" interface to the MCP protocol, but sometimes you may need access to the raw MCP protocol objects. Each of the main client methods that returns data has a corresponding `*_mcp` method that returns the raw MCP protocol objects directly.
+
+```python
+# Standard method - returns just the list of tools
+tools = await client.list_tools()
+# tools -> list[mcp.types.Tool]
+
+# Raw MCP method - returns the full protocol object
+result = await client.list_tools_mcp()
+# result -> mcp.types.ListToolsResult
+tools = result.tools
+```
+
+Available raw MCP methods:
+
+*   **`list_tools_mcp()`**: Returns `mcp.types.ListToolsResult`
+*   **`call_tool_mcp(name, arguments)`**: Returns `mcp.types.CallToolResult`
+*   **`list_resources_mcp()`**: Returns `mcp.types.ListResourcesResult`
+*   **`list_resource_templates_mcp()`**: Returns `mcp.types.ListResourceTemplatesResult`
+*   **`read_resource_mcp(uri)`**: Returns `mcp.types.ReadResourceResult`
+*   **`list_prompts_mcp()`**: Returns `mcp.types.ListPromptsResult`
+*   **`get_prompt_mcp(name, arguments)`**: Returns `mcp.types.GetPromptResult`
+*   **`complete_mcp(ref, argument)`**: Returns `mcp.types.CompleteResult`
+
+These methods are especially useful for debugging or when you need to access metadata or fields that aren't exposed by the simplified methods.
+
 ### Advanced Features
 
 MCP allows servers to interact with clients in order to provide additional capabilities. The `Client` constructor accepts additional configuration to handle these server requests.
@@ -268,5 +296,5 @@ async def safe_call_tool():
 Other errors, like connection failures, will raise standard Python exceptions (e.g., `ConnectionError`, `TimeoutError`). 
 
 <Tip>
-The client transport often has its own error-handling mechanisms, so you can not always trap errors like those raised by `call_tool` outside of the `async with` block. Instead, you can call `call_tool(..., _return_raw_result=True)` to get the raw `mcp.types.CallToolResult` object and handle errors yourself by checking its `isError` attribute.
+The client transport often has its own error-handling mechanisms, so you can not always trap errors like those raised by `call_tool` outside of the `async with` block. Instead, you can use `call_tool_mcp()` to get the raw `mcp.types.CallToolResult` object and handle errors yourself by checking its `isError` attribute.
 </Tip>

src/fastmcp/client/client.py

@@ -1,7 +1,7 @@
 import datetime
 from contextlib import AbstractAsyncContextManager
 from pathlib import Path
-from typing import Any, Literal, cast, overload
+from typing import Any, cast
 
 import mcp.types
 from mcp import ClientSession
@@ -107,6 +107,7 @@ async def __aexit__(self, exc_type, exc_val, exc_tb):
             self._session = None
 
     # --- MCP Client Methods ---
+
     async def ping(self) -> None:
         """Send a ping request."""
         await self.session.send_ping()
@@ -128,23 +129,100 @@ async def send_roots_list_changed(self) -> None:
         """Send a roots/list_changed notification."""
         await self.session.send_roots_list_changed()
 
-    async def list_resources(self) -> list[mcp.types.Resource]:
-        """Send a resources/list request."""
+    # --- Resources ---
+
+    async def list_resources_mcp(self) -> mcp.types.ListResourcesResult:
+        """Send a resources/list request and return the complete MCP protocol result.
+
+        Returns:
+            mcp.types.ListResourcesResult: The complete response object from the protocol,
+                containing the list of resources and any additional metadata.
+
+        Raises:
+            RuntimeError: If called while the client is not connected.
+        """
         result = await self.session.list_resources()
+        return result
+
+    async def list_resources(self) -> list[mcp.types.Resource]:
+        """Retrieve a list of resources available on the server.
+
+        Returns:
+            list[mcp.types.Resource]: A list of Resource objects.
+
+        Raises:
+            RuntimeError: If called while the client is not connected.
+        """
+        result = await self.list_resources_mcp()
         return result.resources
 
-    async def list_resource_templates(self) -> list[mcp.types.ResourceTemplate]:
-        """Send a resources/listResourceTemplates request."""
+    async def list_resource_templates_mcp(
+        self,
+    ) -> mcp.types.ListResourceTemplatesResult:
+        """Send a resources/listResourceTemplates request and return the complete MCP protocol result.
+
+        Returns:
+            mcp.types.ListResourceTemplatesResult: The complete response object from the protocol,
+                containing the list of resource templates and any additional metadata.
+
+        Raises:
+            RuntimeError: If called while the client is not connected.
+        """
         result = await self.session.list_resource_templates()
+        return result
+
+    async def list_resource_templates(
+        self,
+    ) -> list[mcp.types.ResourceTemplate]:
+        """Retrieve a list of resource templates available on the server.
+
+        Returns:
+            list[mcp.types.ResourceTemplate]: A list of ResourceTemplate objects.
+
+        Raises:
+            RuntimeError: If called while the client is not connected.
+        """
+        result = await self.list_resource_templates_mcp()
         return result.resourceTemplates
 
+    async def read_resource_mcp(
+        self, uri: AnyUrl | str
+    ) -> mcp.types.ReadResourceResult:
+        """Send a resources/read request and return the complete MCP protocol result.
+
+        Args:
+            uri (AnyUrl | str): The URI of the resource to read. Can be a string or an AnyUrl object.
+
+        Returns:
+            mcp.types.ReadResourceResult: The complete response object from the protocol,
+                containing the resource contents and any additional metadata.
+
+        Raises:
+            RuntimeError: If called while the client is not connected.
+        """
+        if isinstance(uri, str):
+            uri = AnyUrl(uri)  # Ensure AnyUrl
+        result = await self.session.read_resource(uri)
+        return result
+
     async def read_resource(
         self, uri: AnyUrl | str
     ) -> list[mcp.types.TextResourceContents | mcp.types.BlobResourceContents]:
-        """Send a resources/read request."""
+        """Read the contents of a resource or resolved template.
+
+        Args:
+            uri (AnyUrl | str): The URI of the resource to read. Can be a string or an AnyUrl object.
+
+        Returns:
+            list[mcp.types.TextResourceContents | mcp.types.BlobResourceContents]: A list of content
+                objects, typically containing either text or binary data.
+
+        Raises:
+            RuntimeError: If called while the client is not connected.
+        """
         if isinstance(uri, str):
             uri = AnyUrl(uri)  # Ensure AnyUrl
-        result = await self.session.read_resource(uri)
+        result = await self.read_resource_mcp(uri)
         return result.contents
 
     # async def subscribe_resource(self, uri: AnyUrl | str) -> None:
@@ -159,66 +237,190 @@ async def read_resource(
     #         uri = AnyUrl(uri)
     #     await self.session.unsubscribe_resource(uri)
 
-    async def list_prompts(self) -> list[mcp.types.Prompt]:
-        """Send a prompts/list request."""
+    # --- Prompts ---
+
+    async def list_prompts_mcp(self) -> mcp.types.ListPromptsResult:
+        """Send a prompts/list request and return the complete MCP protocol result.
+
+        Returns:
+            mcp.types.ListPromptsResult: The complete response object from the protocol,
+                containing the list of prompts and any additional metadata.
+
+        Raises:
+            RuntimeError: If called while the client is not connected.
+        """
         result = await self.session.list_prompts()
+        return result
+
+    async def list_prompts(self) -> list[mcp.types.Prompt]:
+        """Retrieve a list of prompts available on the server.
+
+        Returns:
+            list[mcp.types.Prompt]: A list of Prompt objects.
+
+        Raises:
+            RuntimeError: If called while the client is not connected.
+        """
+        result = await self.list_prompts_mcp()
         return result.prompts
 
+    # --- Prompt ---
+    async def get_prompt_mcp(
+        self, name: str, arguments: dict[str, str] | None = None
+    ) -> mcp.types.GetPromptResult:
+        """Send a prompts/get request and return the complete MCP protocol result.
+
+        Args:
+            name (str): The name of the prompt to retrieve.
+            arguments (dict[str, str] | None, optional): Arguments to pass to the prompt. Defaults to None.
+
+        Returns:
+            mcp.types.GetPromptResult: The complete response object from the protocol,
+                containing the prompt messages and any additional metadata.
+
+        Raises:
+            RuntimeError: If called while the client is not connected.
+        """
+        result = await self.session.get_prompt(name=name, arguments=arguments)
+        return result
+
     async def get_prompt(
         self, name: str, arguments: dict[str, str] | None = None
     ) -> list[mcp.types.PromptMessage]:
-        """Send a prompts/get request."""
-        result = await self.session.get_prompt(name, arguments)
+        """Retrieve a rendered prompt message list from the server.
+
+        Args:
+            name (str): The name of the prompt to retrieve.
+            arguments (dict[str, str] | None, optional): Arguments to pass to the prompt. Defaults to None.
+
+        Returns:
+            list[mcp.types.PromptMessage]: A list of prompt messages.
+
+        Raises:
+            RuntimeError: If called while the client is not connected.
+        """
+        result = await self.get_prompt_mcp(name=name, arguments=arguments)
         return result.messages
 
+    # --- Completion ---
+
+    async def complete_mcp(
+        self,
+        ref: mcp.types.ResourceReference | mcp.types.PromptReference,
+        argument: dict[str, str],
+    ) -> mcp.types.CompleteResult:
+        """Send a completion request and return the complete MCP protocol result.
+
+        Args:
+            ref (mcp.types.ResourceReference | mcp.types.PromptReference): The reference to complete.
+            argument (dict[str, str]): Arguments to pass to the completion request.
+
+        Returns:
+            mcp.types.CompleteResult: The complete response object from the protocol,
+                containing the completion and any additional metadata.
+
+        Raises:
+            RuntimeError: If called while the client is not connected.
+        """
+        result = await self.session.complete(ref=ref, argument=argument)
+        return result
+
     async def complete(
         self,
         ref: mcp.types.ResourceReference | mcp.types.PromptReference,
         argument: dict[str, str],
     ) -> mcp.types.Completion:
-        """Send a completion request."""
-        result = await self.session.complete(ref, argument)
+        """Send a completion request to the server.
+
+        Args:
+            ref (mcp.types.ResourceReference | mcp.types.PromptReference): The reference to complete.
+            argument (dict[str, str]): Arguments to pass to the completion request.
+
+        Returns:
+            mcp.types.Completion: The completion object.
+
+        Raises:
+            RuntimeError: If called while the client is not connected.
+        """
+        result = await self.complete_mcp(ref=ref, argument=argument)
         return result.completion
 
-    async def list_tools(self) -> list[mcp.types.Tool]:
-        """Send a tools/list request."""
+    # --- Tools ---
+
+    async def list_tools_mcp(self) -> mcp.types.ListToolsResult:
+        """Send a tools/list request and return the complete MCP protocol result.
+
+        Returns:
+            mcp.types.ListToolsResult: The complete response object from the protocol,
+                containing the list of tools and any additional metadata.
+
+        Raises:
+            RuntimeError: If called while the client is not connected.
+        """
         result = await self.session.list_tools()
+        return result
+
+    async def list_tools(self) -> list[mcp.types.Tool]:
+        """Retrieve a list of tools available on the server.
+
+        Returns:
+            list[mcp.types.Tool]: A list of Tool objects.
+
+        Raises:
+            RuntimeError: If called while the client is not connected.
+        """
+        result = await self.list_tools_mcp()
         return result.tools
 
-    @overload
+    # --- Call Tool ---
+
+    async def call_tool_mcp(
+        self, name: str, arguments: dict[str, Any]
+    ) -> mcp.types.CallToolResult:
+        """Send a tools/call request and return the complete MCP protocol result.
+
+        This method returns the raw CallToolResult object, which includes an isError flag
+        and other metadata. It does not raise an exception if the tool call results in an error.
+
+        Args:
+            name (str): The name of the tool to call.
+            arguments (dict[str, Any]): Arguments to pass to the tool.
+
+        Returns:
+            mcp.types.CallToolResult: The complete response object from the protocol,
+                containing the tool result and any additional metadata.
+
+        Raises:
+            RuntimeError: If called while the client is not connected.
+        """
+        result = await self.session.call_tool(name=name, arguments=arguments)
+        return result
+
     async def call_tool(
         self,
         name: str,
         arguments: dict[str, Any] | None = None,
-        _return_raw_result: Literal[False] = False,
     ) -> list[
         mcp.types.TextContent | mcp.types.ImageContent | mcp.types.EmbeddedResource
-    ]: ...
+    ]:
+        """Call a tool on the server.
 
-    @overload
-    async def call_tool(
-        self,
-        name: str,
-        arguments: dict[str, Any] | None = None,
-        _return_raw_result: Literal[True] = True,
-    ) -> mcp.types.CallToolResult: ...
+        Unlike call_tool_mcp, this method raises a ClientError if the tool call results in an error.
 
-    async def call_tool(
-        self,
-        name: str,
-        arguments: dict[str, Any] | None = None,
-        _return_raw_result: bool = False,
-    ) -> (
-        list[
-            mcp.types.TextContent | mcp.types.ImageContent | mcp.types.EmbeddedResource
-        ]
-        | mcp.types.CallToolResult
-    ):
-        """Send a tools/call request."""
-        result = await self.session.call_tool(name, arguments)
-        if _return_raw_result:
-            return result
-        elif result.isError:
+        Args:
+            name (str): The name of the tool to call.
+            arguments (dict[str, Any] | None, optional): Arguments to pass to the tool. Defaults to None.
+
+        Returns:
+            list[mcp.types.TextContent | mcp.types.ImageContent | mcp.types.EmbeddedResource]:
+                The content returned by the tool.
+
+        Raises:
+            ClientError: If the tool call results in an error.
+            RuntimeError: If called while the client is not connected.
+        """
+        result = await self.call_tool_mcp(name=name, arguments=arguments or {})
+        if result.isError:
             msg = cast(mcp.types.TextContent, result.content[0]).text
             raise ClientError(msg)
         return result.content