Add error handling for JSON marshaling in mcp-go

Author: jboolean

contrib/mark3labs/mcp-go/mcpgo.go

@@ -46,10 +46,16 @@ func NewToolHandlerMiddleware() server.ToolHandlerMiddleware {
 
 			result, err := next(ctx, request)
 
-			inputJSON, _ := json.Marshal(request)
+			inputJSON, marshalErr := json.Marshal(request)
+			if marshalErr != nil {
+				instr.Logger().Warn("mcp-go: failed to marshal tool request: %v", marshalErr)
+			}
 			var outputText string
 			if result != nil {
-				resultJSON, _ := json.Marshal(result)
+				resultJSON, marshalErr := json.Marshal(result)
+				if marshalErr != nil {
+					instr.Logger().Warn("mcp-go: failed to marshal tool result: %v", marshalErr)
+				}
 				outputText = string(resultJSON)
 			}
 
@@ -93,7 +99,10 @@ func (h *hooks) onError(ctx context.Context, id any, method mcp.MCPMethod, messa
 	if !ok {
 		return
 	}
-	inputJSON, _ := json.Marshal(message)
+	inputJSON, marshalErr := json.Marshal(message)
+	if marshalErr != nil {
+		instr.Logger().Warn("mcp-go: failed to marshal error message: %v", marshalErr)
+	}
 	if annotator, ok := span.(textIOAnnotator); ok {
 		annotator.AnnotateTextIO(string(inputJSON), err.Error())
 	}
@@ -109,8 +118,14 @@ func finishSpanWithIO[Req any, Res any](h *hooks, id any, request Req, result Re
 	if !ok {
 		return
 	}
-	inputJSON, _ := json.Marshal(request)
-	resultJSON, _ := json.Marshal(result)
+	inputJSON, marshalErr := json.Marshal(request)
+	if marshalErr != nil {
+		instr.Logger().Warn("mcp-go: failed to marshal request: %v", marshalErr)
+	}
+	resultJSON, marshalErr := json.Marshal(result)
+	if marshalErr != nil {
+		instr.Logger().Warn("mcp-go: failed to marshal result: %v", marshalErr)
+	}
 	outputText := string(resultJSON)
 
 	if annotator, ok := span.(textIOAnnotator); ok {