fix(observability): avoid error status for expected pkgsite results (#25)

Author: garrettladley

internal/mcpserver/tools/register.go

@@ -62,7 +62,9 @@ func (s *service) result(ctx context.Context, result pkgsite.Result, page pkgsit
 	resultAttrs := observability.ResultAttrs{FromCache: result.FromCache, UpstreamURLPresent: result.UpstreamURL != "", ResultCount: len(result.Items)}
 	if result.Error != nil {
 		resultAttrs.ErrorStatusCode = result.Error.StatusCode
-		span.SetStatus(codes.Error, result.Error.Status)
+		if unexpectedPkgsiteStatus(result.Error.StatusCode) {
+			span.SetStatus(codes.Error, result.Error.Status)
+		}
 	}
 	span.SetAttributes(resultAttrs.Attributes()...)
 	opts := envelopeOptions{Source: pkgsite.DefaultBaseURL, UpstreamURL: result.UpstreamURL, ToolName: toolName, NextArgs: nextArgs}
@@ -74,6 +76,10 @@ func (s *service) result(ctx context.Context, result pkgsite.Result, page pkgsit
 	return textResult(singleEnvelope(result, opts)), nil, nil
 }
 
+func unexpectedPkgsiteStatus(statusCode int) bool {
+	return statusCode >= 500
+}
+
 func toolAttrs(toolName string, args map[string]any, result pkgsite.Result) observability.ToolAttrs {
 	return observability.ToolAttrs{
 		ToolName:         toolName,

internal/mcpserver/tools/register_test.go

@@ -0,0 +1,31 @@
+package tools
+
+import (
+	"strconv"
+	"testing"
+)
+
+func TestUnexpectedPkgsiteStatus(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		status int
+		want   bool
+	}{
+		{status: 400, want: false},
+		{status: 404, want: false},
+		{status: 429, want: false},
+		{status: 500, want: true},
+		{status: 503, want: true},
+	}
+
+	for _, tt := range tests {
+		t.Run(strconv.Itoa(tt.status), func(t *testing.T) {
+			t.Parallel()
+
+			if got := unexpectedPkgsiteStatus(tt.status); got != tt.want {
+				t.Fatalf("unexpectedPkgsiteStatus(%d) = %t, want %t", tt.status, got, tt.want)
+			}
+		})
+	}
+}