MCP servers can provide LLM prompt templates to clients.
Server-side implementation:
Use Server.AddPrompt to register a prompt and its handler. The server automatically gains the prompts capability if prompts are added before connecting to a client, or if ServerOptions.HasPrompts is explicitly set. Adding a prompt notifies connected clients via notifications/prompts/list_changed.
Client-side usage:
- List prompts using the
ClientSession.Prompts iterator or ClientSession.ListPrompts. - Retrieve a specific prompt by name using
ClientSession.GetPrompt, providing arguments for expansion. - Listen for changes in the prompt list by setting
ClientOptions.PromptListChangedHandler.
func Example_prompts() {
ctx := context.Background()
promptHandler := func(ctx context.Context, req *mcp.GetPromptRequest) (*mcp.GetPromptResult, error) {
return &mcp.GetPromptResult{
Description: "Hi prompt",
Messages: []*mcp.PromptMessage{
{
Role: "user",
Content: &mcp.TextContent{Text: "Say hi to " + req.Params.Arguments["name"]},
},
},
},
},
},
}, nil
}
// Create a server with a single prompt.
s := mcp.NewServer(&mcp.Implementation{Name: "server", Version: "v0.0.1"}, nil)
prompt := &mcp.Prompt{
Name: "greet",
Arguments: []*mcp.PromptArgument{
{
Name: "name",
Description: "the name of the person to greet",
Required: true,
},
},
}
s.AddPrompt(prompt, promptHandler)
// Create a client.
c := mcp.NewClient(&mcp.Implementation{Name: "client", Version: "v0.0.1"}, nil)
// Connect the server and client.
t1, t2 := mcp.NewInMemoryTransports()
if _, err := s.Connect(ctx, t1, nil); err != nil {
log.Fatal(err)
}
cs, err := c.Connect(ctx, t2, nil)
if err != nil {
log.Fatal(err)
}
defer cs.Close()
// List the prompts.
for p, err := range cs.Prompts(ctx, nil) {
if err != nil {
log.Fatal(err)
}
fmt.Println(p.Name)
}
// Get the prompt.
res, err := cs.GetPrompt(ctx, &mcp.GetPromptParams{
Name: "greet",
Arguments: map[string]string{"name": "Pat"},
})
if err != nil {
log.Fatal(err)
}
for _, msg := range res.Messages {
fmt.Println(msg.Role, msg.Content.(*mcp.TextContent).Text)
}
// Output:
// greet
// user Say hi to Pat
}
