feat: add NewToolResultJSON (#550)

Author: changkun

mcp/utils.go

@@ -253,6 +253,24 @@ func NewToolResultText(text string) *CallToolResult {
 	}
 }
 
+// NewToolResultJSON creates a new CallToolResult with a JSON content.
+func NewToolResultJSON[T any](data T) (*CallToolResult, error) {
+	b, err := json.Marshal(data)
+	if err != nil {
+		return nil, fmt.Errorf("unable to marshal JSON: %w", err)
+	}
+
+	return &CallToolResult{
+		Content: []Content{
+			TextContent{
+				Type: ContentTypeText,
+				Text: string(b),
+			},
+		},
+		StructuredContent: data,
+	}, nil
+}
+
 // NewToolResultStructured creates a new CallToolResult with structured content.
 // It includes both the structured content and a text representation for backward compatibility.
 func NewToolResultStructured(structured any, fallbackText string) *CallToolResult {

www/docs/pages/servers/advanced.mdx

@@ -130,7 +130,7 @@ func handleCreateUser(ctx context.Context, req mcp.CallToolRequest, input UserCr
         Status:    "created",
     }
 
-    return mcp.NewToolResultJSON(output), nil
+    return mcp.NewToolResultJSON(output)
 }
 ```
 
@@ -962,4 +962,4 @@ For complete sampling documentation, see **[Server Sampling Guide](/servers/adva
 ## Next Steps
 
 - **[Client Development](/clients)** - Learn to build MCP clients
-- **[Server Basics](/servers/basics)** - Review fundamental concepts
+- **[Server Basics](/servers/basics)** - Review fundamental concepts

www/docs/pages/transports/http.mdx

@@ -494,7 +494,7 @@ func handleStatelessTool(ctx context.Context, req mcp.CallToolRequest) (*mcp.Cal
         return nil, err
     }
 
-    return mcp.NewToolResultJSON(result), nil
+    return mcp.NewToolResultJSON(result)
 }
 
 // Use external storage for persistence