# MCP Examples

Examples demonstrating Model Context Protocol (MCP) integration with go-micro.

## Examples

### [hello](./hello/) - Minimal Example ⭐ Start Here

The simplest possible MCP-enabled service. Perfect for learning the basics.

**What it shows:**
- Automatic documentation extraction from Go comments
- MCP gateway setup with 3 lines
- Ready for Claude Code

**Run it:**
```bash
cd hello
go run main.go
```

### [crud](./crud/) - CRUD Contact Book

A realistic service with create, read, update, delete, list, and search operations. Shows how to document a full API for agents with `@example` tags, `description` struct tags, validation errors, and partial updates.

**Run it:**
```bash
cd crud
go run main.go
```

### [workflow](./workflow/) - Cross-Service Orchestration

Three services (Inventory, Orders, Notifications) showing how an AI agent orchestrates multi-step workflows: search products, check stock, reserve inventory, place order, send confirmation — all from a single natural language request.

**Run it:**
```bash
cd workflow
go run main.go
```

### [platform](./platform/) - Agent Platform Showcase

A complete platform (Users, Posts, Comments, Mail) mirroring [micro/blog](https://github.com/micro/blog). Shows how existing microservices become agent-accessible with zero code changes — agents can sign up, write posts, comment, tag, and send mail through natural language.

**Run it:**
```bash
cd platform
go run main.go
```

### [documented](./documented/) - Full-Featured Example

Complete example showing all MCP features with a user service.

**What it shows:**
- Multiple endpoints (GetUser, CreateUser)
- Rich documentation with examples
- Per-endpoint auth scopes via `server.WithEndpointScopes()`
- Pre-populated test data
- Production-ready patterns

**Run it:**
```bash
cd documented
go run main.go
```

## Quick Start

### 1. Write Your Service

Add Go doc comments to your handler methods:

```go
// SayHello greets a person by name. Returns a friendly greeting message.
//
// @example {"name": "Alice"}
func (g *Greeter) SayHello(ctx context.Context, req *HelloRequest, rsp *HelloResponse) error {
    rsp.Message = "Hello " + req.Name + "!"
    return nil
}

type HelloRequest struct {
    Name string `json:"name" description:"Person's name to greet"`
}
```

### 2. Register Handler (Auto-Extracts Docs!)

```go
handler := service.Server().NewHandler(new(Greeter))
service.Server().Handle(handler)
```

### 3. Start MCP Gateway

```go
go mcp.ListenAndServe(":3000", mcp.Options{
    Registry: service.Options().Registry,
})
```

## Testing

### HTTP API

```bash
# List tools
curl http://localhost:3000/mcp/tools | jq

# Call a tool
curl -X POST http://localhost:3000/mcp/call \
  -H "Content-Type: application/json" \
  -d '{
    "tool": "greeter.Greeter.SayHello",
    "input": {"name": "Alice"}
  }' | jq
```

### Claude Code (Stdio)

Start MCP server:
```bash
micro mcp serve
```

Add to `~/.claude/claude_desktop_config.json`:
```json
{
  "mcpServers": {
    "my-services": {
      "command": "micro",
      "args": ["mcp", "serve"]
    }
  }
}
```

Restart Claude Code and ask Claude to use your services!

## Features

### ✅ Automatic Documentation Extraction

Just write Go comments - documentation is extracted automatically:

- **Go doc comments** → Tool descriptions
- **@example tags** → Example inputs for AI
- **Struct tags** → Parameter descriptions

### ✅ Multiple Transports

- **Stdio** - For Claude Code (recommended)
- **HTTP/SSE** - For web-based agents

### ✅ MCP Command Line

```bash
# Start MCP server
micro mcp serve              # Stdio (for Claude Code)
micro mcp serve --address :3000  # HTTP/SSE (for web agents)

# List available tools
micro mcp list               # Human-readable list
micro mcp list --json        # JSON output

# Test a tool
micro mcp test <tool-name> '{"key": "value"}'

# Generate documentation
micro mcp docs               # Markdown format
micro mcp docs --format json # JSON format
micro mcp docs --output tools.md  # Save to file

# Export to different formats
micro mcp export langchain   # Python LangChain tools
micro mcp export openapi     # OpenAPI 3.0 spec
micro mcp export json        # Raw JSON definitions
```

For detailed examples, see [CLI Examples](../../cmd/micro/mcp/EXAMPLES.md).

### ✅ Zero Configuration

- No manual tool registration
- No API wrappers
- No code generation
- Just write normal Go code!

### ✅ Per-Tool Auth Scopes

Declare required scopes when registering a handler:

```go
handler := service.Server().NewHandler(
    new(BlogService),
    server.WithEndpointScopes("Blog.Create", "blog:write"),
    server.WithEndpointScopes("Blog.Delete", "blog:admin"),
)
```

Or define scopes at the gateway layer without changing services:

```go
mcp.Serve(mcp.Options{
    Registry: reg,
    Auth:     authProvider,
    Scopes: map[string][]string{
        "blog.Blog.Create": {"blog:write"},
        "blog.Blog.Delete": {"blog:admin"},
    },
})
```

### ✅ Tracing, Rate Limiting & Audit Logging

Every tool call generates a trace ID that propagates through the RPC chain.
Configure rate limiting and audit logging at the gateway:

```go
mcp.Serve(mcp.Options{
    Registry: reg,
    Auth:     authProvider,
    RateLimit: &mcp.RateLimitConfig{
        RequestsPerSecond: 10,
        Burst:             20,
    },
    AuditFunc: func(r mcp.AuditRecord) {
        log.Printf("[audit] trace=%s tool=%s account=%s allowed=%v",
            r.TraceID, r.Tool, r.AccountID, r.Allowed)
    },
})
```

## Documentation

- [Full MCP Documentation](../../internal/website/docs/mcp.md)
- [MCP Gateway Implementation](../../gateway/mcp/)
- [Documentation Guide](../../gateway/mcp/DOCUMENTATION.md)
- [Blog Post](../../internal/website/blog/2.md)

## Learn More

- [Model Context Protocol Spec](https://modelcontextprotocol.io/)
- [Go Micro Documentation](https://go-micro.dev)