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module: "mcp-development"
sourceSha: "f5122f94fbbe9475b72e2a36b04ae3e4ee98a0b7"
generatedAt: "2026-08-20T06:54:23.199Z"
---
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# MCP Server Development

Guide for building Model Context Protocol servers: project structure, tool design, error handling, testing with MCP Inspector, and evaluation patterns.

- Category: tech-specific
- Status: stable
- Tags: mcp, model-context-protocol, tools, servers
- Dependencies: none
- Presets: cloud-agent, full
- Context cost: ~842 tokens (always-loaded rule files)
- Last updated: 2026-08-04T09:16:14-04:00
- Available as a native plugin marketplace entry

## README

# mcp-development

Guide for building Model Context Protocol (MCP) servers.

## What It Does

Installs a rules file covering MCP server development:

- **Project setup** - Language choice (TypeScript recommended), transport selection (stdio vs HTTP)
- **Tool design** - Naming conventions, input schemas with Zod/Pydantic, output design, error messages
- **Tool annotations** - readOnlyHint, destructiveHint, idempotentHint, openWorldHint
- **Implementation patterns** - Shared utilities, authentication, rate limiting
- **Testing** - MCP Inspector usage, build verification, input validation
- **Quality checklist** - Pre-ship verification steps

## Manual Installation

```bash
# Global (all projects)
mkdir -p ~/.claude/rules
cp rules/mcp-development.md ~/.claude/rules/mcp-development.md

# Project-level
mkdir -p .claude/rules
cp rules/mcp-development.md .claude/rules/mcp-development.md
```

## Files

| File | Description |
|------|-------------|
| `rules/mcp-development.md` | MCP server development guide with tool design patterns and quality checklist |


## Files

### rule

#### rules/mcp-development.md

````
# MCP Server Development

Guidelines for building Model Context Protocol (MCP) servers that enable LLMs to interact with external services.

## Project Setup

### Language Choice

- **TypeScript** (recommended): Better SDK quality, type safety, and LLM compatibility. Use `@modelcontextprotocol/sdk`.
- **Python**: Use `fastmcp` for rapid development.

### Transport

- **stdio**: For local servers (CLI tools, desktop integrations)
- **Streamable HTTP**: For remote/shared servers

## Tool Design

### Naming

- Use clear, descriptive names with consistent prefixes per service
- Pattern: `{service}_{action}_{resource}` (e.g., `github_create_issue`, `slack_send_message`)
- Avoid ambiguous names - the LLM reads these to decide which tool to call

### Input Schemas

- Define strict schemas with Zod (TypeScript) or Pydantic (Python)
- Include constraints (min/max, enums, patterns) in the schema itself
- Add descriptions to every field - these become the tool's documentation for the LLM
- Include examples in field descriptions for complex types

### Output Design

- Return focused, relevant data (not raw API dumps)
- Support filtering and pagination for list operations
- Use structured output schemas when the consumer needs to parse results programmatically

### Error Messages

- Make errors actionable: tell the LLM what went wrong AND what to try next
- Include the specific constraint that was violated
- Suggest alternative tool calls when appropriate
- Never return raw stack traces or internal error details

## Tool Annotations

Annotate every tool to help clients make safety decisions:

```typescript
{
  readOnlyHint: true,      // Does not modify external state
  destructiveHint: false,  // Does not delete or overwrite
  idempotentHint: true,    // Safe to retry
  openWorldHint: false     // Interacts with external services
}
```

## Implementation Patterns

### Shared Utilities

Create reusable modules for:
- API client with auth, rate limiting, and retry logic
- Error formatting (consistent structure across all tools)
- Response formatting (pagination, truncation, summarization)
- Input validation helpers

### Authentication

- Support environment variables for API keys/tokens
- Document required credentials clearly in the README
- Never log or expose credentials in error messages

### Rate Limiting

- Implement client-side rate limiting to stay within API quotas
- Return clear errors when rate limited (include retry-after timing if available)

## Testing

### MCP Inspector

Use `npx @modelcontextprotocol/inspector` to:
- Verify tool schemas are correctly defined
- Test tool execution with sample inputs
- Confirm error handling works as expected

### Build Verification

- Run the build (`npm run build` / type checking) before testing
- Test every tool with both valid and invalid inputs
- Verify error messages are helpful and actionable

## Quality Checklist

Before shipping an MCP server:

- [ ] Every tool has a clear description and annotated inputs
- [ ] Error messages guide the LLM toward resolution
- [ ] Authentication is via environment variables (not hardcoded)
- [ ] Rate limiting prevents API quota exhaustion
- [ ] Tool annotations (readOnly, destructive, idempotent) are set correctly
- [ ] README documents all tools, required credentials, and setup steps
- [ ] Inspector testing confirms all tools work

````