Prompt validation errors are logged with an unnecessary traceback

[rookie-z]

Initial Checks

• I confirm that I'm using the newest release of my line (the latest 2.x, or the latest 1.x if I'm still on v1)
• I confirm that I searched for my issue in https://github.com/modelcontextprotocol/python-sdk/issues before opening this issue

Release line

2.x (current stable)

Description

Description

When a prompt is called without a required argument, the request is correctly rejected, but the Python SDK logs the validation error with a full traceback.

To Reproduce

Steps to reproduce the behavior:

1. Create a prompt with a required argument:

   @mcp.prompt()
   def diagnose_cluster(problem: str) -> str:
       return f"Diagnose: {problem}"

2. Call prompts/list and confirm that problem is marked as required.

3. Call prompts/get without providing the required argument:

   {
     "method": "prompts/get",
     "params": {
       "name": "diagnose_cluster"
     }
   }

4. The request is rejected, but the server logs a full traceback:

   Error getting prompt diagnose_cluster
   Traceback (most recent call last):
     ...
     File ".../mcp/server/mcpserver/server.py", line 1285, in get_prompt
       rendered = await prompt.render(arguments, context)
     File ".../mcp/server/mcpserver/prompts/base.py", line 160, in render
       raise ValueError(f"Missing required arguments: {missing}")
   ValueError: Missing required arguments: {'problem'}
   
   handler for 'prompts/get' raised
   

Example Code

Python & MCP Python SDK

## Environment

- MCP Python SDK: v2
- Python: 3.x
- Server: `MCPServer`
- Prompt transport: Streamable HTTP

[StarsExpress]

Hi, I'd like to work on this issue #3342. My proposed fix:

Inside get_prompt, distinguish expected validation failure ValueError from unexpected exceptions in error-handling path —

• Log ValueError via logger.warning without exc_info.
• Unexpected exceptions keep full traceback with exc_info=True as before.

Will also add a regression test that calls prompts/get with a missing required argument, and asserts no traceback is logged.

Happy to be assigned — thank you.