feature: support creating tools using go-struct-style input schema #535
Description
Problem Statement
Since we’ve already implemented the output schema with structured content, I’m now working on defining the input schema in a similar style.
We can specify JSON Schema properties directly in our Go structsq, such as required, and then use a helper like mcp.WithInputSchema[WeatherRequest]() to generate the input schema accordingly.
This enhancement will help developers maintain MCP services more effectively by enabling a consistent, structured approach to both input and output schemas.
Example Usage
Define a struct for your input:
type WeatherRequest struct {
Location string `json:"location,required" jsonschema_description:"City or location"`
Units string `json:"units,omitempty" jsonschema_description:"celsius or fahrenheit" jsonschema:"enum=celsius,enum=fahrenheit"`
}Define a struct for your output:
type WeatherResponse struct {
Location string `json:"location" jsonschema_description:"The location"`
Temperature float64 `json:"temperature" jsonschema_description:"Current temperature"`
Conditions string `json:"conditions" jsonschema_description:"Weather conditions"`
}Add it to your tool:
tool := mcp.NewTool("get_weather",
mcp.WithDescription("Get weather information"),
mcp.WithInputSchema[WeatherRequest](),
mcp.WithOutputSchema[WeatherResponse](),
)Return structured data in tool result:
func weatherHandler(ctx context.Context, request mcp.CallToolRequest, args WeatherRequest) (*mcp.CallToolResult, error) {
response := WeatherResponse{
Location: args.Location,
Temperature: 25.0,
Conditions: "Cloudy",
}
fallbackText := fmt.Sprintf("Weather in %s: %.1f°C, %s",
response.Location, response.Temperature, response.Conditions)
return mcp.NewToolResultStructured(response, fallbackText), nil
}