MCP Builder

MCP Server Development Guide

Overview

Create MCP (Model Context Protocol) servers that enable LLMs to interact with external services through well-designed tools. The quality of an MCP server is measured by how well it enables LLMs to accomplish real-world tasks.

High-Level Workflow

Phase 1: Deep Research and Planning

API Coverage vs. Workflow Tools: Balance comprehensive API endpoint coverage with specialized workflow tools. When uncertain, prioritize comprehensive API coverage.

Tool Naming and Discoverability: Use consistent prefixes (e.g., github_create_issue, github_list_repos) and action-oriented naming.

Context Management: Design tools that return focused, relevant data. Support pagination where applicable.

Actionable Error Messages: Error messages should guide agents toward solutions with specific suggestions.

Phase 2: Implementation

Recommended Stack:

• Language: TypeScript
• Transport: Streamable HTTP for remote servers, stdio for local servers

For each tool:

1. Input Schema: Use Zod (TypeScript) or Pydantic (Python)
2. Output Schema: Define outputSchema where possible
3. Tool Description: Concise summary of functionality
4. Implementation: Async/await, proper error handling, pagination support
5. Annotations: readOnlyHint, destructiveHint, idempotentHint

Phase 3: Review and Test

• No duplicated code (DRY principle)
• Consistent error handling
• Full type coverage
• Clear tool descriptions

Testing:

# TypeScript
npm run build
npx @modelcontextprotocol/inspector

# Python
python -m py_compile your_server.py

Phase 4: Create Evaluations

Create 10 evaluation questions to test effectiveness:

• Independent, read-only, complex, realistic
• Verifiable with single clear answer
• Stable over time

SDK Documentation

TypeScript SDK: https://github.com/modelcontextprotocol/typescript-sdk Python SDK: https://github.com/modelcontextprotocol/python-sdk MCP Specification: https://modelcontextprotocol.io