Tutorial 1

Server

Demonstrates how to create and configure an MCP server using finemcp.NewServer.

Demonstrates how to create and configure an MCP server using finemcp.NewServer.

How It Works

An MCP server is the core component that:

Registers tools, resources, and prompts
Handles the JSON-RPC 2.0 protocol (initialize, tools/call, resources/read, etc.)
Binds to a transport (HTTP, SSE, WebSocket, stdio) to communicate with clients

The MCP session lifecycle:

Client                        Server
  |── initialize ──────────→    |   Negotiate capabilities & protocol version
  |←──── initialize response ── |
  |── initialized (notif) ──→  |   Client confirms ready
  |── tools/list ──────────→   |   Normal requests begin
  |←──── tools/list response ── |
  |── tools/call ──────────→   |
  |←──── tools/call response ── |

Examples

basic/

The simplest possible MCP server — one tool, one transport.

s := finemcp.NewServer("basic-server", "1.0.0")

tool, _ := finemcp.NewTool("hello",
    func(ctx context.Context, input []byte) ([]byte, error) {
        return []byte("Hello from FineMCP!"), nil
    },
    finemcp.WithDescription("Says hello"),
)
s.RegisterTool(tool)

log.Fatal(transport.StartHTTP(s, ":8080"))

Run: go run ./01-server/basic

options/

Demonstrates all ServerOption variants:

s := finemcp.NewServer("options-demo", "1.0.0",
    finemcp.WithResourceSubscriptions(),     // Enable resource change notifications
    finemcp.WithTaskStore(store),             // Enable async task tracking
    finemcp.WithStreamBufferSize(128),        // Buffer size for streaming responses
    finemcp.WithMaxSessionTools(20),          // Max tools per session overlay
    finemcp.WithMaxSessions(100),             // Max concurrent sessions
    finemcp.WithSupportedVersions("2025-11-25", "2025-03-26"), // Protocol versions
)

Run: go run ./01-server/options

Server Options Reference

Option	Description
`WithResourceSubscriptions()`	Enables `resources/subscribe` and `resources/unsubscribe`
`WithTaskStore(store)`	Enables async task execution with a task store
`WithStreamBufferSize(n)`	Sets the channel buffer size for streaming tool responses
`WithMaxSessionTools(n)`	Limits the number of per-session tool overlays
`WithMaxSessions(n)`	Limits the number of concurrent sessions
`WithSupportedVersions(v...)`	Declares which MCP protocol versions are supported

Testing with curl

# Start the server
go run ./01-server/basic

# Initialize (required first step for every session)
curl -X POST http://localhost:8080 -H "Content-Type: application/json" -d '{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "initialize",
  "params": {
    "protocolVersion": "2025-03-26",
    "clientInfo": { "name": "curl-client", "version": "1.0.0" },
    "capabilities": {}
  }
}'

# List tools
curl -X POST http://localhost:8080 -H "Content-Type: application/json" -d '{
  "jsonrpc": "2.0",
  "id": 2,
  "method": "tools/list"
}'

# Call a tool
curl -X POST http://localhost:8080 -H "Content-Type: application/json" -d '{
  "jsonrpc": "2.0",
  "id": 3,
  "method": "tools/call",
  "params": { "name": "hello" }
}'

Note: initialize can only be called once per session. Restart the server to reset.