Resource Templates of FastMCP server not visible/usable with python-sdk based client

[wanderingnature]

Describe the bug
A clear and concise description of what the bug is.
Implement a client using the python-sdk.
Implement a FastMCP server exposing resource templates
python-sdk based client cannot display resource templates exposed by FastMCP server...

After fixing #129 this bug is exposed when using a client based on python-sdk and a server based on FastMCP.

To Reproduce
Steps to reproduce the behavior:

Implement simple MCP sever exposing a resource template:

#easy_echo.py
"""
FastMCP Echo Server
Implements resource template
"""

from mcp.server.fastmcp import FastMCP

\# Create server
mcp = FastMCP("Easy Echo Server")

@mcp.resource("template://resource/{text}/{more_text}", description="resource template")
def resource_template(text: str, more_text: str) -> str:
    """function name becomes the name"""
    return f"text: {text}, more_text {more_text}"

Implement a simple MCP client to connect to the server and return the resource template

from mcp import ClientSession, StdioServerParameters
from mcp.client.stdio import stdio_client

\# Create server parameters for stdio connection
server_params = StdioServerParameters(
    command=".venv/bin/uv",  # Executable
    args=["run", "--with", "mcp", "mcp", "run", "examples/fastmcp/easy_echo.py"],  # Properly split args
    env={"PATH": ".venv/bin"}  # Use dictionary for env variables
)


async def run():
    async with stdio_client(server_params) as (read, write):
        async with ClientSession(read, write) as session:
            # Initialize the connection
            await session.initialize()


            \# List available resource templates
            resource_templates = await session.list_resource_templates()
            print(f"{resource_templates=}") # raw list_resource_templates() result
            \# Extract relevant data
            templates = resource_templates.resourceTemplates
            print("\nAvailable Resource Templates:")
            for template in templates:
                print(f"🔹 Name: {template.name}")
                print(f"   🔗 URI: {template.uriTemplate}")
                print(f"   📜 Description: {template.description}")
                print()

            \# Read a resource template
            resource = await session.read_resource("template://resource/hello_world/more_text")
            print(f"{resource=}") # raw read_resource() results
            print(f"   🔗 URI: {resource.contents[0].uri}")
            print(f"   📜 Result: {resource.contents[0].text}")
            print()


if __name__ == "__main__":
    import asyncio
    asyncio.run(run())

run the client test:

python examples/fastmcp/easy_test.py 

Expected behavior
/resource/templates/list returns resource templates
(output from easy_test.py AFTER implementing simple correction in src/mcp/client/session.py)

raw output

resource=ReadResourceResult(meta=None, contents=[TextResourceContents(uri=AnyUrl('template://resource/hello_world/more_text'), mimeType='text/plain', text='text: hello_world, more_text more_text')])

structured output

1. resources/templates/list
Request:
{
  "method": "resources/templates/list",
  "params": {}
}

Response:
{
  "resourceTemplates": [
    {
      "uriTemplate": "template://resource/{text}/{more_text}",
      "name": "resource_template",
      "description": "resource template"
    }
  ]
}

output from easy_test.py

Processing request of type ListResourceTemplatesRequest                                                                            server.py:638
resource_templates=ListResourceTemplatesResult(meta=None, nextCursor=None, resourceTemplates=[])

Available Resource Templates:
                    INFO     Processing request of type ReadResourceRequest                                                                                     server.py:638
resource=ReadResourceResult(meta=None, contents=[TextResourceContents(uri=AnyUrl('template://resource/hello_world/more_text'), mimeType='text/plain', text='text: hello_world, more_text more_text')])
   🔗 URI: template://resource/hello_world/more_text
   📜 Result: text: hello_world, more_text more_text

Note that the inspector is implemented in typescript and will return a valid response template regardless of whether session.py is fixed.

Actual behavior
Throws error: (thrown by easy_test.py)

[01/07/25 08:35:55] INFO     Processing request of type ListResourcesRequest                                                                                    server.py:638
resources=ListResourcesResult(meta=None, nextCursor=None, resources=[])

Available Resources:
  + Exception Group Traceback (most recent call last):
  |   File "src/mcp/client/stdio.py", line 153, in stdio_client
  |     yield read_stream, write_stream
  |   File "examples/fastmcp/easy_test.py", line 14, in run
  |     async with ClientSession(read, write) as session:
  |   File "src/mcp/shared/session.py", line 122, in __aexit__
  |     return await self._task_group.__aexit__(exc_type, exc_val, exc_tb)
  |   File ".venv/lib/python3.10/site-packages/anyio/_backends/_asyncio.py", line 685, in __aexit__
  |     raise BaseExceptionGroup(
  | exceptiongroup.ExceptionGroup: unhandled errors in a TaskGroup (1 sub-exception)
  +-+---------------- 1 ----------------
    | Traceback (most recent call last):
    |   File "examples/fastmcp/easy_test.py", line 38, in run
    |     resource_templates = await session.list_resource_templates()
    | AttributeError: 'ClientSession' object has no attribute 'list_resource_templates'

ADD TO: src/mcp/client/session.py

    async def list_resource_templates(self) -> types.ListResourceTemplatesResult:
        """Send a resources/templates/list request."""
        return await self.send_request(
            types.ClientRequest(
                types.ListResourceTemplatesRequest(
                    method="resources/templates/list",
                )
            ),
            types.ListResourceTemplatesResult,
        )

Desktop (please complete the following information):

• OS: Mac OS Monterey
• Browser Chrome

Additional context
Although this will enable list_resource_templates, and the use of resource templates, with a custom client based on the python-sdk there does not appear to be any support for resource templates in the Claude Desktop Client - I have tested with both python-sdk and fastmcp based servers.

I understand this is not specifically a FastMCP issue, but clients may currently only be built with the python-sdk and thus clients are unable to utilize resource templates provided by FastMCP.

[dsp-ant]

This was fixed in 0d3e02f