Prompts

Prompts enable servers to define reusable prompt templates and workflows that clients can easily surface to users and LLMs

MCP prompts is a concept of MCP servers. Server should list prompts when requested with method prompts/list and retrieve when requested with method prompts/get.

Foxy Contexts allows easy way to define a prompt and register it within fx DI container.

NewPrompt

In order to create new prompt you shall use fxctx.NewPrompt function. It accepts prompt name, description and function that would be called when prompt is called.

examples/simple_prompt/main.go 
func NewGreatPrompt() fxctx.Prompt {
	return fxctx.NewPrompt(
		// This information about the prompt would be used when it is listed:
		mcp.Prompt{
			Name:        "my-great-prompt",
			Description: Ptr("Doing something great"),
			Arguments: []mcp.PromptArgument{
				{
					Description: Ptr("An argument for the prompt"),
					Name:        "arg-1",
					Required:    Ptr(true),
				},
			},
		},
		// This is the callback that would be executed when the prompt/get is requested:
		func(_ context.Context, req *mcp.GetPromptRequest) (*mcp.GetPromptResult, error) {
			description := "Prompting to do something great"
			return &mcp.GetPromptResult{
				Description: &description,
				Messages: []mcp.PromptMessage{
					{
						Content: mcp.TextContent{
							Type: "text",
							Text: "Would you like to do something great?",
						},
						Role: mcp.RoleUser,
					},
				},
			}, nil
		},
	)
}

Register prompt and start server

examples/simple_prompt/main.go 
func main() {
	app.
		NewBuilder().
		// adding the tool to the app
		WithPrompt(NewGreatPrompt).
		// setting up server
		WithName("great-tool-server").
		WithVersion("0.0.1").
		WithTransport(stdio.NewTransport()).
		// Configuring fx logging to only show errors
		WithFxOptions(
			fx.Provide(func() *zap.Logger {
				cfg := zap.NewDevelopmentConfig()
				cfg.Level.SetLevel(zap.ErrorLevel)
				logger, _ := cfg.Build()
				return logger
			}),
			fx.Option(fx.WithLogger(
				func(logger *zap.Logger) fxevent.Logger {
					return &fxevent.ZapLogger{Logger: logger}
				},
			)),
		).Run()
}

Examples

Check out complete example of MCP Server with prompt:

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