# 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. Use when this capability is needed.

- Skill: `tomevault-io/mcp-expert` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add tomevault-io/mcp-expert`
- Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/mcp-expert/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Data & Analytics
- Author: tomevault-io (https://skillmd.com/u/tomevault-io)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/tomevault-io/mcp-expert

---


# 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)
```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

```typescript
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

```typescript
// 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
1. **Validate all inputs** with Zod schemas
2. **Use parameterized queries** - never concatenate SQL
3. **Principle of least privilege** for database users
4. **Rate limit** expensive operations
5. **Sanitize** sensitive data in outputs

### Tool Design
1. **Single Responsibility**: One tool = one specific operation
2. **Descriptive Names**: `sql_select`, `file_read`, not `query` or `do`
3. **Clear Descriptions**: Claude uses descriptions to decide when to use tools
4. **Detailed Schemas**: Use `.describe()` on every Zod field
5. **Explicit Limits**: maxRows, timeout, maxSize

### Error Handling
```typescript
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).

```typescript
console.error("[MCP] Tool called:", toolName);
console.error("[MCP] Result:", JSON.stringify(result));
```

## Claude Configuration

```json
{
  "mcpServers": {
    "server-name": {
      "command": "node",
      "args": ["path/to/build/index.js"],
      "env": {
        "DB_HOST": "localhost",
        "DB_NAME": "mydb"
      }
    }
  }
}
```

## Testing

```bash
# Use MCP Inspector for interactive testing
npx @modelcontextprotocol/inspector
```

---
> Source: [fabriciofs/mcp-sql-server](https://github.com/fabriciofs/mcp-sql-server) — distributed by [TomeVault](https://tomevault.io).
<!-- tomevault:4.0:skill_md:2026-06-16 -->