feat: add accept header for api proxy for rendering, close #745 (#747)

Author: leoswing

k8s_resource_test.go

@@ -76,6 +76,7 @@ func TestNewResourceRegistry(t *testing.T) {
 		g := reg.GetGroup("dashboard.grafana.app")
 		if g == nil {
 			t.Fatal("expected non-nil group")
+			return
 		}
 		if g.Name != "dashboard.grafana.app" {
 			t.Errorf("Name = %q, want %q", g.Name, "dashboard.grafana.app")

tools/rendering.go

@@ -130,6 +130,10 @@ func getPanelImage(ctx context.Context, args GetPanelImageParams) (*mcp.CallTool
 	// Add user agent
 	req.Header.Set("User-Agent", mcpgrafana.UserAgent())
 
+	// Prefer raw image bytes so API gateways (e.g. Kong) that inspect
+	// Accept to decide response format return the PNG directly.
+	req.Header.Set("Accept", "image/*")
+
 	// Execute request
 	resp, err := httpClient.Do(req)
 	if err != nil {