Agent skill
mcp-expert
Expert in Model Context Protocol (MCP) server development. Use when building MCP servers, creating tools for Claude, implementing resources, debugging MCP connections, or integrating databases with Claude Code.
Install this agent skill to your Project
npx add-skill https://github.com/majiayu000/claude-skill-registry/tree/main/skills/development/mcp-expert
SKILL.md
MCP (Model Context Protocol) Expert
You are an expert in developing MCP servers for integration with Claude and other LLMs.
MCP Architecture
Core Concepts
- Tools: Functions that Claude can invoke (operations, queries, actions)
- Resources: Static or dynamic data exposed to Claude (files, templates)
- Prompts: Pre-defined prompt templates
- Transports: stdio (default), HTTP/SSE, WebSocket
SDK Setup (TypeScript)
import { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js";
import { StdioServerTransport } from "@modelcontextprotocol/sdk/server/stdio.js";
import { z } from "zod";
const server = new McpServer({
name: "my-mcp-server",
version: "1.0.0",
});
Tool Structure
server.registerTool(
"tool_name",
{
description: `Clear description of what the tool does.
When to use:
- Use case 1
- Use case 2
Limitations:
- Limitation 1`,
inputSchema: z.object({
param: z.string().describe("Parameter description"),
limit: z.number().int().positive().max(1000).default(100)
.describe("Max results (default: 100, max: 1000)"),
}),
},
async (args) => {
const result = await operation(args);
return {
content: [{ type: "text", text: JSON.stringify(result, null, 2) }],
structuredContent: result,
};
}
);
Return Format
// Success
return {
content: [{ type: "text", text: "Human readable result" }],
structuredContent: { data: "Machine readable" },
};
// Error
return {
content: [{ type: "text", text: `Error: ${error.message}` }],
isError: true,
};
Best Practices
Security
- Validate all inputs with Zod schemas
- Use parameterized queries - never concatenate SQL
- Principle of least privilege for database users
- Rate limit expensive operations
- Sanitize sensitive data in outputs
Tool Design
- Single Responsibility: One tool = one specific operation
- Descriptive Names:
sql_select,file_read, notqueryordo - Clear Descriptions: Claude uses descriptions to decide when to use tools
- Detailed Schemas: Use
.describe()on every Zod field - Explicit Limits: maxRows, timeout, maxSize
Error Handling
try {
const result = await db.query(sql);
return { content: [{ type: "text", text: JSON.stringify(result) }] };
} catch (error) {
console.error("[MCP] Error:", error);
return {
content: [{ type: "text", text: `Query failed: ${error.message}` }],
isError: true,
};
}
Logging
Important: Use console.error for logs in stdio servers (stdout is for protocol).
console.error("[MCP] Tool called:", toolName);
console.error("[MCP] Result:", JSON.stringify(result));
Claude Configuration
{
"mcpServers": {
"server-name": {
"command": "node",
"args": ["path/to/build/index.js"],
"env": {
"DB_HOST": "localhost",
"DB_NAME": "mydb"
}
}
}
}
Testing
# Use MCP Inspector for interactive testing
npx @modelcontextprotocol/inspector
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