chore(roo): add pic-gen mode rules, update mcp.json and new-mcp-server skill

.roo/skills/new-mcp-server/SKILL.md

@@ -30,14 +30,23 @@ touch mcp/{name}/src/__init__.py
 ```
 
 ### Step 2 — Write `mcp/{name}/src/server.py`
+
+**Convention:** All tool parameters **must** use `Annotated[type, Field(description="...")]` for
+descriptions. Do **not** use docstring `Args:` sections — FastMCP reads `Field` metadata directly
+to expose parameter descriptions in the MCP schema.
+
 ```python
+from typing import Annotated
 from fastmcp import FastMCP
+from pydantic import Field
 
 mcp = FastMCP("mcp-{name}")
 
 @mcp.tool()
-def {tool_name}(param: str) -> str:
-    """Tool description."""
+def {tool_name}(
+    param: Annotated[str, Field(description="What this parameter controls")],
+) -> str:
+    """One-line tool description (no Args: section needed)."""
     # implementation
     ...
 
@@ -45,6 +54,8 @@ if __name__ == "__main__":
     mcp.run()
 ```
 
+> Optional parameters with defaults: `param: Annotated[int, Field(description="...")] = 10`
+
 ### Step 3 — Write `mcp/{name}/pyproject.toml`
 ```toml
 [project]