MCP Builder

MCP Builder

Create MCP servers that let agents interact with external services through clean tools.

Process

1. Research

• Review the MCP specification at https://modelcontextprotocol.io/sitemap.xml.
• Fetch the TypeScript or Python SDK README from GitHub.
• Read the target API docs to identify endpoints, auth, pagination, and data models.

2. Plan

• List the tools to implement. Prefer comprehensive API coverage over one-off workflow tools.
• Use consistent, action-oriented names with prefixes, e.g. github_create_issue, github_list_repos.
• Decide transport: streamable HTTP for remote, stdio for local.

3. Implement

TypeScript (default)

• Use the MCP SDK with Zod for input schemas.
• Define outputSchema and structuredContent where supported.
• Annotate tools with readOnlyHint, destructiveHint, idempotentHint, openWorldHint.

Python

• Use FastMCP with Pydantic models.
• Add @mcp.tool() decorators.

Shared rules:

• Async I/O for network calls.
• Actionable error messages.
• Pagination on list operations.
• Return both text and structured data when possible.

4. Test

• Build and run the server.
• Test with the MCP Inspector:

npx @modelcontextprotocol/inspector

5. Evaluate

Create 10 read-only, complex, realistic questions that require multiple tool calls. Verify answers yourself. Store as evals.xml or evals/evals.json.

Reference

• references/mcp-best-practices.md — server and tool conventions
• references/node-mcp-server.md — TypeScript patterns
• references/python-mcp-server.md — Python patterns
• references/evaluation.md — evaluation guidelines