Handle list tools with no body (#55)

go.mod

@@ -14,6 +14,7 @@ require (
 	github.com/buger/jsonparser v1.1.1 // indirect
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/mailru/easyjson v0.7.7 // indirect
+	github.com/pkg/errors v0.9.1 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
 	github.com/tidwall/gjson v1.18.0 // indirect
 	github.com/tidwall/match v1.1.1 // indirect

go.sum

@@ -11,6 +11,8 @@ github.com/invopop/jsonschema v0.12.0/go.mod h1:ffZ5Km5SWWRAIN6wbDXItl95euhFz2uO
 github.com/josharian/intern v1.0.0/go.mod h1:5DoeVV0s6jJacbCEi61lwdGj/aVlrQvzHFFd8Hwg//Y=
 github.com/mailru/easyjson v0.7.7 h1:UGYAvKxe3sBsEDzO8ZeWOSlIQfWFlxbzLZe7hwFURr0=
 github.com/mailru/easyjson v0.7.7/go.mod h1:xzfreul335JAWq5oZzymOObrkdz5UnU4kGfJJLY9Nlc=
+github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
+github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/stretchr/testify v1.9.0 h1:HtqpIVDClZ4nwg75+f6Lvsy/wHu+3BoSGCbBAcpTsTg=

server.go

@@ -9,6 +9,7 @@ import (
 	"github.com/metoro-io/mcp-golang/internal/protocol"
 	"github.com/metoro-io/mcp-golang/internal/tools"
 	"github.com/metoro-io/mcp-golang/transport"
+	"github.com/pkg/errors"
 	"reflect"
 	"sort"
 	"strings"
@@ -319,19 +320,19 @@ func createWrappedPromptHandler(userHandler any) func(baseGetPromptRequestParams
 		// Unmarshal the JSON into the correct type
 		err := json.Unmarshal(arguments.Arguments, &unmarshaledArguments)
 		if err != nil {
-			return newPromptResponseSentError(fmt.Errorf("failed to unmarshal arguments: %w", err))
+			return newPromptResponseSentError(errors.Wrap(err, "failed to unmarshal arguments"))
 		}
 
 		// Need to dereference the unmarshaled arguments
 		of := reflect.ValueOf(unmarshaledArguments)
 		if of.Kind() != reflect.Ptr || !of.Elem().CanInterface() {
-			return newPromptResponseSentError(fmt.Errorf("arguments must be a struct"))
+			return newPromptResponseSentError(errors.Wrap(err, "arguments must be a struct"))
 		}
 		// Call the handler with the typed arguments
 		output := handlerValue.Call([]reflect.Value{of.Elem()})
 
 		if len(output) != 2 {
-			return newPromptResponseSentError(fmt.Errorf("handler must return exactly two values, got %d", len(output)))
+			return newPromptResponseSentError(errors.New(fmt.Sprintf("handler must return exactly two values, got %d", len(output))))
 		}
 
 		if !output[0].CanInterface() {
@@ -437,40 +438,40 @@ func createWrappedToolHandler(userHandler any) func(baseCallToolRequestParams) *
 	return func(arguments baseCallToolRequestParams) *toolResponseSent {
 		// Instantiate a struct of the type of the arguments
 		if !reflect.New(argumentType).CanInterface() {
-			return newToolResponseSentError(fmt.Errorf("arguments must be a struct"))
+			return newToolResponseSentError(errors.Wrap(fmt.Errorf("arguments must be a struct"), "failed to create argument struct"))
 		}
 		unmarshaledArguments := reflect.New(argumentType).Interface()
 
 		// Unmarshal the JSON into the correct type
 		err := json.Unmarshal(arguments.Arguments, &unmarshaledArguments)
 		if err != nil {
-			return newToolResponseSentError(fmt.Errorf("failed to unmarshal arguments: %w", err))
+			return newToolResponseSentError(errors.Wrap(err, "failed to unmarshal arguments"))
 		}
 
 		// Need to dereference the unmarshaled arguments
 		of := reflect.ValueOf(unmarshaledArguments)
 		if of.Kind() != reflect.Ptr || !of.Elem().CanInterface() {
-			return newToolResponseSentError(fmt.Errorf("arguments must be a struct"))
+			return newToolResponseSentError(errors.Wrap(fmt.Errorf("arguments must be a struct"), "failed to dereference arguments"))
 		}
 		// Call the handler with the typed arguments
 		output := handlerValue.Call([]reflect.Value{of.Elem()})
 
 		if len(output) != 2 {
-			return newToolResponseSentError(fmt.Errorf("handler must return exactly two values, got %d", len(output)))
+			return newToolResponseSentError(errors.Wrap(fmt.Errorf("handler must return exactly two values, got %d", len(output)), "invalid handler return"))
 		}
 
 		if !output[0].CanInterface() {
-			return newToolResponseSentError(fmt.Errorf("handler must return a struct, got %s", output[0].Type().Name()))
+			return newToolResponseSentError(errors.Wrap(fmt.Errorf("handler must return a struct, got %s", output[0].Type().Name()), "invalid handler return"))
 		}
 		tool := output[0].Interface()
 		if !output[1].CanInterface() {
-			return newToolResponseSentError(fmt.Errorf("handler must return an error, got %s", output[1].Type().Name()))
+			return newToolResponseSentError(errors.Wrap(fmt.Errorf("handler must return an error, got %s", output[1].Type().Name()), "invalid handler return"))
 		}
 		errorOut := output[1].Interface()
 		if errorOut == nil {
 			return newToolResponseSent(tool.(*ToolResponse))
 		}
-		return newToolResponseSentError(errorOut.(error))
+		return newToolResponseSentError(errors.Wrap(errorOut.(error), "handler returned an error"))
 	}
 }
 
@@ -514,9 +515,13 @@ func (s *Server) handleListTools(request *transport.BaseJSONRPCRequest, _ protoc
 		Cursor *string `json:"cursor"`
 	}
 	var params toolRequestParams
-	err := json.Unmarshal(request.Params, &params)
-	if err != nil {
-		return nil, fmt.Errorf("failed to unmarshal arguments: %w", err)
+	if request.Params == nil {
+		params = toolRequestParams{}
+	} else {
+		err := json.Unmarshal(request.Params, &params)
+		if err != nil {
+			return nil, errors.Wrap(err, "failed to unmarshal arguments")
+		}
 	}
 
 	// Order by name for pagination
@@ -534,7 +539,7 @@ func (s *Server) handleListTools(request *transport.BaseJSONRPCRequest, _ protoc
 		// Base64 decode the cursor
 		c, err := base64.StdEncoding.DecodeString(*params.Cursor)
 		if err != nil {
-			return nil, fmt.Errorf("failed to decode cursor: %w", err)
+			return nil, errors.Wrap(err, "failed to decode cursor")
 		}
 		cString := string(c)
 		// Iterate through the tools until we find an entry > the cursor
@@ -585,7 +590,7 @@ func (s *Server) handleToolCalls(req *transport.BaseJSONRPCRequest, _ protocol.R
 	// Instantiate a struct of the type of the arguments
 	err := json.Unmarshal(req.Params, &params)
 	if err != nil {
-		return nil, fmt.Errorf("failed to unmarshal arguments: %w", err)
+		return nil, errors.Wrap(err, "failed to unmarshal arguments")
 	}
 
 	var toolToUse *tool
@@ -598,11 +603,10 @@ func (s *Server) handleToolCalls(req *transport.BaseJSONRPCRequest, _ protocol.R
 	})
 
 	if toolToUse == nil {
-		return nil, fmt.Errorf("unknown tool: %s", req.Method)
+		return nil, errors.Wrapf(err, "unknown tool: %s", req.Method)
 	}
 	return toolToUse.Handler(params), nil
 }
-
 func (s *Server) generateCapabilities() serverCapabilities {
 	t := false
 	return serverCapabilities{
@@ -623,15 +627,14 @@ func (s *Server) generateCapabilities() serverCapabilities {
 		}(),
 	}
 }
-
 func (s *Server) handleListPrompts(request *transport.BaseJSONRPCRequest, extra protocol.RequestHandlerExtra) (transport.JsonRpcBody, error) {
 	type promptRequestParams struct {
 		Cursor *string `json:"cursor"`
 	}
 	var params promptRequestParams
 	err := json.Unmarshal(request.Params, &params)
 	if err != nil {
-		return nil, fmt.Errorf("failed to unmarshal arguments: %w", err)
+		return nil, errors.Wrap(err, "failed to unmarshal arguments")
 	}
 
 	// Order by name for pagination
@@ -649,7 +652,7 @@ func (s *Server) handleListPrompts(request *transport.BaseJSONRPCRequest, extra
 		// Base64 decode the cursor
 		c, err := base64.StdEncoding.DecodeString(*params.Cursor)
 		if err != nil {
-			return nil, fmt.Errorf("failed to decode cursor: %w", err)
+			return nil, errors.Wrap(err, "failed to decode cursor")
 		}
 		cString := string(c)
 		// Iterate through the prompts until we find an entry > the cursor
@@ -694,7 +697,7 @@ func (s *Server) handleListResources(request *transport.BaseJSONRPCRequest, extr
 	var params resourceRequestParams
 	err := json.Unmarshal(request.Params, &params)
 	if err != nil {
-		return nil, fmt.Errorf("failed to unmarshal arguments: %w", err)
+		return nil, errors.Wrap(err, "failed to unmarshal arguments")
 	}
 
 	// Order by URI for pagination
@@ -712,7 +715,7 @@ func (s *Server) handleListResources(request *transport.BaseJSONRPCRequest, extr
 		// Base64 decode the cursor
 		c, err := base64.StdEncoding.DecodeString(*params.Cursor)
 		if err != nil {
-			return nil, fmt.Errorf("failed to decode cursor: %w", err)
+			return nil, errors.Wrap(err, "failed to decode cursor")
 		}
 		cString := string(c)
 		// Iterate through the resources until we find an entry > the cursor
@@ -760,7 +763,7 @@ func (s *Server) handlePromptCalls(req *transport.BaseJSONRPCRequest, extra prot
 	// Instantiate a struct of the type of the arguments
 	err := json.Unmarshal(req.Params, &params)
 	if err != nil {
-		return nil, fmt.Errorf("failed to unmarshal arguments: %w", err)
+		return nil, errors.Wrap(err, "failed to unmarshal arguments")
 	}
 
 	var promptToUse *prompt
@@ -773,7 +776,7 @@ func (s *Server) handlePromptCalls(req *transport.BaseJSONRPCRequest, extra prot
 	})
 
 	if promptToUse == nil {
-		return nil, fmt.Errorf("unknown prompt: %s", req.Method)
+		return nil, errors.Wrapf(err, "unknown prompt: %s", req.Method)
 	}
 	return promptToUse.Handler(params), nil
 }
@@ -783,7 +786,7 @@ func (s *Server) handleResourceCalls(req *transport.BaseJSONRPCRequest, extra pr
 	// Instantiate a struct of the type of the arguments
 	err := json.Unmarshal(req.Params, &params)
 	if err != nil {
-		return nil, fmt.Errorf("failed to unmarshal arguments: %w", err)
+		return nil, errors.Wrap(err, "failed to unmarshal arguments")
 	}
 
 	var resourceToUse *resource
@@ -796,7 +799,7 @@ func (s *Server) handleResourceCalls(req *transport.BaseJSONRPCRequest, extra pr
 	})
 
 	if resourceToUse == nil {
-		return nil, fmt.Errorf("unknown prompt: %s", req.Method)
+		return nil, errors.Wrapf(err, "unknown prompt: %s", req.Method)
 	}
 	return resourceToUse.Handler(), nil
 }