mcp-server-template: Instructions file for GitHub Copilot

Copilot Instructions

Build, Test & Lint

npm run build          # TypeScript compilation (tsc)
npm test               # Run all tests (vitest)
npm run test:watch     # Watch mode
npm run test:coverage  # With coverage report
npm run lint           # ESLint on src/ and scripts/
npm run format:check   # Prettier check
npm run format         # Prettier auto-fix
npm run validate       # Run all CI checks (format, lint, build, test:coverage)

Important: Always run npm run validate after making changes to ensure nothing is broken. This runs the same checks as CI.

Run a single test file:

npx vitest run src/__tests__/server.test.ts

Run a single test by name:

npx vitest run -t "should return a greeting"

Architecture

This is an MCP (Model Context Protocol) server that exposes tools for AI assistants. It communicates over stdio transport.

Key Source Files

• src/index.ts — Entry point. Creates the MCP server and connects it via StdioServerTransport.
• src/server.ts — Registers all MCP tools with Zod schemas. This is where tool definitions and handlers live.

Adding a New Tool

Edit src/server.ts and register a new tool using server.tool(). See the existing hello tool for the pattern.

Conventions

• Formatting: Prettier with no semicolons, single quotes, trailing commas (es5), 100 char print width.
• Commit messages: Follow conventional commits (feat:, fix:, chore:, docs:, test:).
• Test coverage: Maintain above 90%. Tests live in src/__tests__/ mirroring source file names.
• Integration tests: Use InMemoryTransport.createLinkedPair() from the MCP SDK to test server tools end-to-end without stdio.
• ESM: The project uses ES modules ("type": "module" in package.json). Use .js extensions in TypeScript import paths.
• Tool responses: All MCP tool handlers return { content: [{ type: 'text' as const, text: string }] }. Error responses add isError: true.