Fix MCP tool/prompt calls failing with non-serializable framework arguments

[Copilot]

Motivation and Context

MCP call_tool() and get_prompt() methods were attempting to serialize framework-internal arguments like response_format (a Python type), causing serialization failures when these parameters were passed through the function invocation pipeline.

Description

Added filtering to exclude non-serializable framework kwargs before passing to MCP SDK:

• call_tool method: Added response_format to existing exclusion set and improved formatting for readability
• get_prompt method: Added same filtering logic (previously missing)

Framework kwargs now filtered:

{"chat_options", "tools", "tool_choice", "thread", "conversation_id", "options", "response_format"}

Tests added:

• test_mcp_tool_filters_framework_kwargs() - validates tool call filtering
• test_mcp_prompt_filters_framework_kwargs() - validates prompt call filtering

Both tests verify that only actual tool/prompt parameters are passed to MCP session, while framework kwargs are stripped.

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the Contribution Guidelines
• All unit tests pass, and I have added new tests where possible
• Is this a breaking change? If yes, add "[BREAKING]" prefix to the title of the PR.

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Original prompt

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This section details on the original issue you should resolve

<issue_title>.NET: Python: [Bug]: MCP tool call fails with non-serializable arguments (response_format)</issue_title>
<issue_description>### Description

Bug Description

When calling an MCP tool with additional parameters like response_format, the call_tool method in _mcp.py fails because these non-serializable arguments are not filtered out before being passed to session.call_tool().

Expected Behavior

The filtered_kwargs should exclude non-serializable arguments before calling session.call_tool().

Suggested Fix

Add response_format to the exclusion list around line 762 in _mcp.py.

Code Sample

Error Messages / Stack Traces

2026-01-27 00:57:23,667 DEBUG agent_framework: Function arguments: {'code': 'import pypsa\n\n# Create an empty network\nnetwork = pypsa.Network()\n\n# Add buses to the network\nnetwork.add("Bus", "Bus 1", x=0, y=0)\nnetwork.add("Bus", "Bus 2", x=1, y=0)\nnetwork.add("Bus", "Bus 3", x=2, y=0)\n\n# Add lines between buses\nnetwork.add("Line", "Line 1", bus0="Bus 1", bus1="Bus 2", length=1.0, x=0.1, r=0.01)\nnetwork.add("Line", "Line 2", bus0="Bus 2", bus1="Bus 3", length=1.0, x=0.1, r=0.01)\n\n# Add a generator at Bus 1\nnetwork.add("Generator", "Generator 1", bus="Bus 1", p_nom=100, marginal_cost=50)\n\n# Add a load at Bus 3\nnetwork.add("Load", "Load 1", bus="Bus 3", p_set=50)\n\n# Save the network as a NetCDF file for further analysis\nnetwork_path = get_output_path("small_power_grid.nc", "powergrid")\nnetwork.export_to_netcdf(network_path)\n\nprint(f"Power grid saved to: {network_path}")', 'timeout': 1500, 'response_format': <class 'core.agent.response_models.AgentResponse'>, 'thread': <agent_framework._threads.AgentThread object at 0x72738273a660>}
2026-01-27 00:57:23,667 DEBUG agent_framework: Failed to call tool 'execute_powergrid_code'.
Traceback (most recent call last):
File "/home/danrongzhang/agora/agora/AgoraAgentMAF/.venv/lib/python3.13/site-packages/agent_framework/_mcp.py", line 768, in call_tool
result = await self.session.call_tool(tool_name, arguments=filtered_kwargs) # type: ignore
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/danrongzhang/agora/agora/AgoraAgentMAF/.venv/lib/python3.13/site-packages/mcp/client/session.py", line 383, in call_tool
result = await self.send_request(
^^^^^^^^^^^^^^^^^^^^^^^^
...<8 lines>...
)
^
File "/home/danrongzhang/agora/agora/AgoraAgentMAF/.venv/lib/python3.13/site-packages/mcp/shared/session.py", line 263, in send_request
request_data = request.model_dump(by_alias=True, mode="json", exclude_none=True)
File "/home/danrongzhang/agora/agora/AgoraAgentMAF/.venv/lib/python3.13/site-packages/pydantic/main.py", line 464, in model_dump
return self.pydantic_serializer.to_python(
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^
self,
^^^^^

Package Versions

agent-framework 1.0.0b260123

Python Version

python 3.13.2

Additional Context

No response</issue_description>

<agent_instructions>Analyse this error and update the issue with your findings</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes .NET: Python: [Bug]: MCP tool call fails with non-serializable arguments (response_format) #3466

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