nts; they are used to execute code or otherwise produce a side effect) - Define interaction patterns through **Prompts** (reusable templates for LLM interactions) - And more! ## Core Concepts ### Server

Show Server Examples

The server is your core interface to the MCP protocol. It handles connection management, protocol compliance, and message routing: ```go // Create a basic server s := server.NewMCPServer( "My Server", // Server name "1.0.0", // Version ) // Start the server using stdio if err := server.ServeStdio(s); err != nil { log.Fatalf("Server error: %v", err) } ```

### Resources

Show Resource Examples

Resources are how you expose data to LLMs. They can be anything - files, API responses, database queries, system information, etc. Resources can be: - Static (fixed URI) - Dynamic (using URI templates) Here's a simple example of a static resource: ```go // Static resource example - exposing a README file resource := mcp.NewResource( "docs://readme", "Project README", mcp.WithResourceDescription("The project's README file"), mcp.WithMIMEType("text/markdown"), ) // Add resource with its handler s.AddResource(resource, func(ctx context.Context, request mcp.ReadResourceRequest) ([]mcp.ResourceContents, error) { content, err := os.ReadFile("README.md") if err != nil { return nil, err } return []mcp.ResourceContents{ mcp.TextResourceContents{ URI: "docs://readme", MIMEType: "text/markdown", Text: string(content), }, }, nil }) ``` And here's an example of a dynamic resource using a template: ```go // Dynamic resource example - user profiles by ID template := mcp.NewResourceTemplate( "users://{id}/profile", "User Profile", mcp.WithTemplateDescription("Returns user profile information"), mcp.WithTemplateMIMEType("application/json"), ) // Add template with its handler s.AddResourceTemplate(template, func(ctx context.Context, request mcp.ReadResourceRequest) ([]mcp.ResourceContents, error) { // Extract ID from the URI using regex matching // The server automatically matches URIs to templates userID := extractIDFromURI(request.Params.URI) profile, err := getUserProfile(userID) // Your DB/API call here if err != nil { return nil, err } return []mcp.ResourceContents{ mcp.TextResourceContents{ URI: request.Params.URI, MIMEType: "application/json", Text: profile, }, }, nil }) ``` The examples are simple but demonstrate the core concepts. Resources can be much more sophisticated - serving multiple contents, integrating with databases or external APIs, etc.

### Tools

Show Tool Examples

Tools let LLMs take actions through your server. Unlike resources, tools are expected to perform computation and have side effects. They're similar to POST endpoints in a REST API. Simple calculation example: ```go calculatorTool := mcp.NewTool("calculate", mcp.WithDescription("Perform basic arithmetic calculations"), mcp.WithString("operation", mcp.Required(), mcp.Description("The arithmetic operation to perform"), mcp.Enum("add", "subtract", "multiply", "divide"), ), mcp.WithNumber("x", mcp.Required(), mcp.Description("First number"), ), mcp.WithNumber("y", mcp.Required(), mcp.Description("Second number"), ), ) s.AddTool(calculatorTool, func(ctx context.Context, request mcp.CallToolRequest) (*mcp.CallToolResult, error) { op := request.Params.Arguments["operation"].(string) x := request.Params.Arguments["x"].(float64) y := request.Params.Arguments["y"].(float64) var result float64 switch op { case "add": result = x + y case "subtract": result = x - y case "multiply": result = x * y case "divide": if y == 0 {

MCP Go 🚀

Tools