feat: add execution parameter to add_tool() for task support declaration

[jief123]

Summary

Add execution parameter to MCPServer.add_tool(), ToolManager.add_tool(), and Tool.from_function() to allow declaring execution.taskSupport per tool as required by MCP spec 2025-11-25.

Also pass execution through in MCPServer.list_tools() when converting internal Tool to MCP types.Tool.

Motivation and Context

The MCP spec (2025-11-25) requires tools to declare task support via execution.taskSupport in the tools/list response:

In the result of tools/list, tools declare support for tasks via execution.taskSupport, which if present can have a value of "required", "optional", or "forbidden".

While server.experimental.enable_tasks() correctly handles server-level capabilities and task handler registration, there is currently no way to set execution.taskSupport on individual tools through the high-level API. This means tools always appear as taskSupport: "forbidden" to clients, even when the server supports tasks.

Usage

from mcp.types import ToolExecution, TASK_OPTIONAL

mcp.add_tool(
    my_handler,
    name="long_running_tool",
    description="A tool that takes a while",
    execution=ToolExecution(taskSupport=TASK_OPTIONAL),
)

Changes

• src/mcp/server/mcpserver/tools/base.py — Add execution field to Tool model and execution parameter to Tool.from_function()
• src/mcp/server/mcpserver/tools/tool_manager.py — Add execution parameter to ToolManager.add_tool() and pass through to Tool.from_function()
• src/mcp/server/mcpserver/server.py — Add execution parameter to MCPServer.add_tool(), pass through to ToolManager.add_tool(), and include execution=info.execution in list_tools() conversion

Breaking Changes

None. The execution parameter is optional and defaults to None, preserving existing behavior.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed

References

• Fixes MCPServer.add_tool() missing execution parameter for task support declaration (spec compliance gap) #2156
• MCP Spec 2025-11-25 — Tasks: Tool-Level Negotiation
• SEP-1686 Tasks implementation PR #1645