mcp: align PromptHandler args with other handlers (#348)

The second arg is a GetPromptRequest.

Fixes #300.

Author: jba

examples/server/hello/main.go

@@ -30,11 +30,11 @@ func SayHi(ctx context.Context, req *mcp.CallToolRequest, args HiArgs) (*mcp.Cal
 	}, nil, nil
 }
 
-func PromptHi(ctx context.Context, ss *mcp.ServerSession, params *mcp.GetPromptParams) (*mcp.GetPromptResult, error) {
+func PromptHi(ctx context.Context, req *mcp.GetPromptRequest) (*mcp.GetPromptResult, error) {
 	return &mcp.GetPromptResult{
 		Description: "Code review prompt",
 		Messages: []*mcp.PromptMessage{
-			{Role: "user", Content: &mcp.TextContent{Text: "Say hi to " + params.Arguments["name"]}},
+			{Role: "user", Content: &mcp.TextContent{Text: "Say hi to " + req.Params.Arguments["name"]}},
 		},
 	}, nil
 }

mcp/client_list_test.go

@@ -126,6 +126,6 @@ func testIterator[T any](t *testing.T, seq iter.Seq2[*T, error], want []*T) {
 	}
 }
 
-func testPromptHandler(context.Context, *mcp.ServerSession, *mcp.GetPromptParams) (*mcp.GetPromptResult, error) {
+func testPromptHandler(context.Context, *mcp.GetPromptRequest) (*mcp.GetPromptResult, error) {
 	panic("not implemented")
 }

mcp/mcp_test.go

@@ -47,11 +47,11 @@ var codeReviewPrompt = &Prompt{
 	Arguments:   []*PromptArgument{{Name: "Code", Required: true}},
 }
 
-func codReviewPromptHandler(_ context.Context, _ *ServerSession, params *GetPromptParams) (*GetPromptResult, error) {
+func codReviewPromptHandler(_ context.Context, req *GetPromptRequest) (*GetPromptResult, error) {
 	return &GetPromptResult{
 		Description: "Code review prompt",
 		Messages: []*PromptMessage{
-			{Role: "user", Content: &TextContent{Text: "Please review the following code: " + params.Arguments["Code"]}},
+			{Role: "user", Content: &TextContent{Text: "Please review the following code: " + req.Params.Arguments["Code"]}},
 		},
 	}, nil
 }
@@ -103,7 +103,7 @@ func TestEndToEnd(t *testing.T) {
 			return nil, nil, errTestFailure
 		})
 	s.AddPrompt(codeReviewPrompt, codReviewPromptHandler)
-	s.AddPrompt(&Prompt{Name: "fail"}, func(_ context.Context, _ *ServerSession, _ *GetPromptParams) (*GetPromptResult, error) {
+	s.AddPrompt(&Prompt{Name: "fail"}, func(_ context.Context, _ *GetPromptRequest) (*GetPromptResult, error) {
 		return nil, errTestFailure
 	})
 	s.AddResource(resource1, readHandler)

mcp/prompt.go

@@ -9,7 +9,7 @@ import (
 )
 
 // A PromptHandler handles a call to prompts/get.
-type PromptHandler func(context.Context, *ServerSession, *GetPromptParams) (*GetPromptResult, error)
+type PromptHandler func(context.Context, *GetPromptRequest) (*GetPromptResult, error)
 
 type serverPrompt struct {
 	prompt  *Prompt

mcp/server.go

@@ -446,7 +446,7 @@ func (s *Server) getPrompt(ctx context.Context, req *GetPromptRequest) (*GetProm
 			Message: fmt.Sprintf("unknown prompt %q", req.Params.Name),
 		}
 	}
-	return prompt.handler(ctx, req.Session, req.Params)
+	return prompt.handler(ctx, req)
 }
 
 func (s *Server) listTools(_ context.Context, req *ListToolsRequest) (*ListToolsResult, error) {