Function main

examples/server/middleware/main.go:19–148

This example demonstrates server side logging using the mcp.Middleware system.

()

// This example demonstrates server side logging using the mcp.Middleware system.
func main() {
	// Create a logger for demonstration purposes.
	logger := slog.New(slog.NewTextHandler(os.Stdout, &slog.HandlerOptions{
		Level: slog.LevelInfo,
		ReplaceAttr: func(_ []string, a slog.Attr) slog.Attr {
			// Simplify timestamp format for consistent output.
			if a.Key == slog.TimeKey {
				return slog.String("time", "2025-01-01T00:00:00Z")
			}
			return a
		},
	}))

	loggingMiddleware := func(next mcp.MethodHandler) mcp.MethodHandler {
		return func(
			ctx context.Context,
			method string,
			req mcp.Request,
		) (mcp.Result, error) {
			logger.Info("MCP method started",
				"method", method,
				"session_id", req.GetSession().ID(),
				"has_params", req.GetParams() != nil,
			)
			// Log more for tool calls.
			if ctr, ok := req.(*mcp.CallToolRequest); ok {
				logger.Info("Calling tool",
					"name", ctr.Params.Name,
					"args", ctr.Params.Arguments)
			}

			start := time.Now()
			result, err := next(ctx, method, req)
			duration := time.Since(start)
			if err != nil {
				logger.Error("MCP method failed",
					"method", method,
					"session_id", req.GetSession().ID(),
					"duration_ms", duration.Milliseconds(),
					"err", err,
				)
			} else {
				logger.Info("MCP method completed",
					"method", method,
					"session_id", req.GetSession().ID(),
					"duration_ms", duration.Milliseconds(),
					"has_result", result != nil,
				)
				// Log more for tool results.
				if ctr, ok := result.(*mcp.CallToolResult); ok {
					logger.Info("tool result",
						"isError", ctr.IsError,
						"structuredContent", ctr.StructuredContent)
				}
			}
			return result, err
		}
	}