t1k:unity:base:mcp-tool-creator

Field	Value
Module	`base`
Version	`2.2.2`
Effort	`medium`
Tools	—

Keywords: bridge, MCP, tool creator, unity

How to invoke

/t1k:unity:base:mcp-tool-creator
[tool-name] [description]

Unity MCP Tool Creator

Create/update MCP tools for the Unity MCP package (e.g., Packages/com.coplaydev.unity-mcp).

Scope

Handles: MCP tool creation (C# + Python), tool updates, action-based routing, parameter handling. Does NOT handle: MCP server infrastructure, transport layer, middleware, resource creation.

Architecture

Each MCP tool requires 2 files:

Packages/[your-mcp-package]/
  MCPForUnity/Editor/Tools/Manage<Domain>.cs    # C# — handles commands in Unity Editor
  Server/src/services/tools/manage_<domain>.py  # Python — MCP tool definition for LLM clients

Auto-discovery: C# uses [McpForUnityTool] attribute; Python uses @mcp_for_unity_tool decorator. Both auto-register — no manual wiring needed.

Step-by-Step Workflow

Create Manage<Domain>.cs with [McpForUnityTool] attribute and HandleCommand(JObject params)
Route actions via switch expression: action switch { "do_x" => DoX(p), _ => ErrorResponse }
Create manage_<domain>.py with @mcp_for_unity_tool decorator and typed Annotated params
Send params via send_with_unity_instance → return {"success": bool, "message": str, "data": ...}
Verify: check Unity console for compile errors, test each action, confirm Python server logs registration

→ See references/tool-templates.md for complete C# and Python file templates.

Key API — C# Parameter Helpers

p.GetRequired("action")   // Result<string> — check .IsSuccess
p.Get("key", "default")   // string with fallback
p.GetBool("key", false)   // bool
p.GetInt("key")           // int?

Response types: SuccessResponse("msg", data), ErrorResponse("msg"), PendingResponse("msg", poll)

→ See references/tool-templates.md for full ToolParams API, response types, attribute options, conventions.

Conventions

Naming: ManageFoo (C#) → manage_foo (Python) → manage_foo (MCP tool name)
Action-based routing: All tools use action as first discriminator
Editor-only: All C# code under Editor/ — never reference from Runtime
Studio tools: Create new files, don’t modify upstream — minimizes merge conflicts

Gotchas

C# handler must be in Editor folder: [McpForUnityTool] classes must live under Editor/ — placing them in Runtime/ causes build errors since they reference UnityEditor APIs
Python registration path must match: The Python file name manage_<domain>.py must match the tool name used in @mcp_for_unity_tool. Mismatches cause the tool to not register
Tool name collisions: If two packages register the same tool name, only one loads. Prefix studio tools with a unique namespace (e.g., studio_manage_x) to avoid conflicts with upstream MCP tools

Reference Files

File	Contents
`references/tool-templates.md`	Full C# + Python templates, ToolParams API, conventions, verification