#8. File & Component Creation Rules

#New File Locations

#Checklist for Adding a New Tool

1. src/tools/<name>.ts — define the tool with toolDef() (description, inputSchema, handler). Every inputSchema field must be .nullable() with a .describe() that states its default — see 04-coding-rules
2. src/tools/index.ts — merge the new tool into the tools object
3. src/tools/<name>.test.ts — unit test for the handler
4. src/tools/openai-schema.test.ts — bump the tool count so the guard covers the new tool
5. README.md — add the argument table, defaults, ranges, return shape and examples by hand
6. skills/mcp-kit-cli/SKILL.md — add the same argument table by hand
7. The exposed name field is part of MCP client compatibility — choose it carefully

#Decision Guide for Modifying Existing Components

#When to Extract Shared Logic

Extract to shared logic if any of these conditions apply:

1. Same code used by both the MCP server and the CLI → Move to src/common/kit/
2. Same code used in 2+ tools → Extract to a utility in the owning domain directory (e.g., src/exchange/parse.ts)
3. Complex Zod schema reused → Extract to a shared Zod schema

#Common Naming Rules