Merge pull request #242 from buildkite/fix/trace-tool-name-and-otel-service-name

fix(trace): restore mcp.tool_name span attribute and fix OTel service name

Author: wolfeidau

pkg/trace/middleware.go

@@ -22,6 +22,10 @@ func NewMiddleware() mcp.Middleware {
 				attribute.String("mcp.session_id", sessionID),
 			}
 
+			if params, ok := req.GetParams().(*mcp.CallToolParamsRaw); ok && params != nil {
+				attrs = append(attrs, attribute.String("mcp.tool_name", params.Name))
+			}
+
 			var clientName, clientVersion string
 			if ss, ok := req.GetSession().(*mcp.ServerSession); ok {
 				if ip := ss.InitializeParams(); ip != nil && ip.ClientInfo != nil && ip.ClientInfo.Name != "" {

pkg/trace/middleware_test.go

@@ -80,6 +80,7 @@ func TestNewMiddleware(t *testing.T) {
 	assert.Contains(attrs, "mcp.session_id", "mcp.session_id attribute should be set")
 	assert.Equal("test-client", attrs["mcp.client.name"], "mcp.client.name should be captured from initialize handshake")
 	assert.Equal("v0.0.1", attrs["mcp.client.version"], "mcp.client.version should be captured from initialize handshake")
+	assert.Equal("ping", attrs["mcp.tool_name"], "mcp.tool_name should be set for tools/call requests")
 }
 
 func TestNewMiddlewareHTTP(t *testing.T) {
@@ -109,4 +110,5 @@ func TestNewMiddlewareHTTP(t *testing.T) {
 	assert.NotEmpty(attrs["mcp.session_id"], "mcp.session_id should be non-empty over HTTP transport")
 	assert.Equal("test-client", attrs["mcp.client.name"], "mcp.client.name should be captured from initialize handshake")
 	assert.Equal("v0.0.1", attrs["mcp.client.version"], "mcp.client.version should be captured from initialize handshake")
+	assert.Equal("ping", attrs["mcp.tool_name"], "mcp.tool_name should be set for tools/call requests")
 }

pkg/trace/trace.go

@@ -18,8 +18,8 @@ import (
 	"go.opentelemetry.io/otel/trace"
 )
 
-// set a default tracer name
-var tracerName = "buildkite-mcp-server"
+// tracerName is the instrumentation library name, fixed for this package.
+const tracerName = "buildkite-mcp-server"
 
 func NewProvider(ctx context.Context, exporter, name, version string) (*sdktrace.TracerProvider, error) {
 	exp, err := newExporter(ctx, exporter)
@@ -45,8 +45,6 @@ func NewProvider(ctx context.Context, exporter, name, version string) (*sdktrace
 		),
 	)
 
-	tracerName = name
-
 	return tp, nil
 }
 
@@ -100,6 +98,7 @@ func newResource(cxt context.Context, name, version string) (*resource.Resource,
 	options = append(options, resource.WithHost())
 	options = append(options, resource.WithFromEnv())
 	options = append(options, resource.WithAttributes(
+		semconv.ServiceNameKey.String(name),
 		semconv.TelemetrySDKNameKey.String("otelconfig"),
 		semconv.TelemetrySDKLanguageGo,
 		semconv.TelemetrySDKVersionKey.String(version),