UEMCP: Skill for Claude Code

UEMCP Manifest Generator Type Hint Compatibility

Problem

The UEMCP dynamic tool manifest generator (plugin/Content/Python/ops/tool_manifest.py) uses typing.get_origin() to detect Optional[T] parameters and generate correct JSON Schema. Python 3.10+ introduced str | None as shorthand for Optional[str], but these produce types.UnionType — which typing.get_origin() does NOT recognize as Union.

This means parameters typed as str | None silently fall through to the default {"type": "string"} without being detected as optional, causing them to appear as required in the MCP tool schema.

Context / Trigger Conditions

• Adding new ops modules to UEMCP with Python 3.10+ type hints
• Parameters using X | None instead of Optional[X]
• Tools appear in manifest but optional parameters show as required
• No error is raised — the failure is completely silent

Solution

For PARAMETER type hints (processed by the manifest generator): Always use Optional[X] from typing, never X | None:

from typing import Any, Optional

def my_tool(
    required_param: str,           # Required - no default
    optional_param: Optional[str] = None,  # Correctly detected as optional
    # NOT: optional_param: str | None = None  # BROKEN - silently treated as required string
) -> dict[str, Any]:  # Return types are fine with modern syntax
    ...

For RETURN type hints (not processed by the manifest generator): Modern syntax is fine — use dict[str, Any], list[str], etc.

Why This Happens

# tool_manifest.py line 79-80
origin = get_origin(python_type)
if origin is Union:  # Only matches typing.Union, NOT types.UnionType

• get_origin(Optional[str]) returns typing.Union (match)
• get_origin(str | None) returns types.UnionType (no match)

The parameter falls through all checks and hits the default: return {"type": "string"}

Verification

After adding a new ops module, check the manifest output:

from ops.tool_manifest import get_tool_manifest
manifest = get_tool_manifest()
# Find your tool and verify optional params are NOT in the "required" array
tool = next(t for t in manifest['tools'] if t['name'] == 'your_tool_name')
print(tool['inputSchema']['required'])  # Should not include optional params