Fix tool calls (#38)

* set all capabilities to off and auto enable if items are added

* update checks and tests

Author: ezynda3

server/server.go

@@ -163,27 +163,39 @@ type toolCapabilities struct {
 // WithResourceCapabilities configures resource-related server capabilities
 func WithResourceCapabilities(subscribe, listChanged bool) ServerOption {
 	return func(s *MCPServer) {
-		s.capabilities.resources = &resourceCapabilities{
-			subscribe:   subscribe,
-			listChanged: listChanged,
+		if !subscribe && !listChanged {
+			s.capabilities.resources = nil
+		} else {
+			s.capabilities.resources = &resourceCapabilities{
+				subscribe:   subscribe,
+				listChanged: listChanged,
+			}
 		}
 	}
 }
 
 // WithPromptCapabilities configures prompt-related server capabilities
 func WithPromptCapabilities(listChanged bool) ServerOption {
 	return func(s *MCPServer) {
-		s.capabilities.prompts = &promptCapabilities{
-			listChanged: listChanged,
+		if !listChanged {
+			s.capabilities.prompts = nil
+		} else {
+			s.capabilities.prompts = &promptCapabilities{
+				listChanged: listChanged,
+			}
 		}
 	}
 }
 
 // WithToolCapabilities configures tool-related server capabilities
 func WithToolCapabilities(listChanged bool) ServerOption {
 	return func(s *MCPServer) {
-		s.capabilities.tools = &toolCapabilities{
-			listChanged: listChanged,
+		if !listChanged {
+			s.capabilities.tools = nil
+		} else {
+			s.capabilities.tools = &toolCapabilities{
+				listChanged: listChanged,
+			}
 		}
 	}
 }
@@ -211,9 +223,9 @@ func NewMCPServer(
 		notificationHandlers: make(map[string]NotificationHandlerFunc),
 		notifications:        make(chan ServerNotification, 100),
 		capabilities: serverCapabilities{
-			tools:     &toolCapabilities{},
-			resources: &resourceCapabilities{},
-			prompts:   &promptCapabilities{},
+			tools:     nil,
+			resources: nil,
+			prompts:   nil,
 			logging:   false,
 		},
 	}
@@ -325,7 +337,7 @@ func (s *MCPServer) HandleMessage(
 		}
 		return s.handleListResourceTemplates(ctx, baseMessage.ID, request)
 	case "resources/read":
-		if !s.capabilities.resources.listChanged {
+		if s.capabilities.resources == nil {
 			return createErrorResponse(
 				baseMessage.ID,
 				mcp.METHOD_NOT_FOUND,
@@ -359,7 +371,7 @@ func (s *MCPServer) HandleMessage(
 		}
 		return s.handleListPrompts(ctx, baseMessage.ID, request)
 	case "prompts/get":
-		if !s.capabilities.prompts.listChanged {
+		if s.capabilities.prompts == nil {
 			return createErrorResponse(
 				baseMessage.ID,
 				mcp.METHOD_NOT_FOUND,
@@ -376,7 +388,7 @@ func (s *MCPServer) HandleMessage(
 		}
 		return s.handleGetPrompt(ctx, baseMessage.ID, request)
 	case "tools/list":
-		if len(s.tools) == 0 {
+		if s.capabilities.tools == nil {
 			return createErrorResponse(
 				baseMessage.ID,
 				mcp.METHOD_NOT_FOUND,
@@ -393,7 +405,7 @@ func (s *MCPServer) HandleMessage(
 		}
 		return s.handleListTools(ctx, baseMessage.ID, request)
 	case "tools/call":
-		if !s.capabilities.tools.listChanged || len(s.tools) == 0 {
+		if s.capabilities.tools == nil {
 			return createErrorResponse(
 				baseMessage.ID,
 				mcp.METHOD_NOT_FOUND,
@@ -424,7 +436,7 @@ func (s *MCPServer) AddResource(
 	handler ResourceHandlerFunc,
 ) {
 	if s.capabilities.resources == nil {
-		panic("Resource capabilities not enabled")
+		s.capabilities.resources = &resourceCapabilities{}
 	}
 	s.mu.Lock()
 	defer s.mu.Unlock()
@@ -440,7 +452,7 @@ func (s *MCPServer) AddResourceTemplate(
 	handler ResourceTemplateHandlerFunc,
 ) {
 	if s.capabilities.resources == nil {
-		panic("Resource capabilities not enabled")
+		s.capabilities.resources = &resourceCapabilities{}
 	}
 	s.mu.Lock()
 	defer s.mu.Unlock()
@@ -453,7 +465,7 @@ func (s *MCPServer) AddResourceTemplate(
 // AddPrompt registers a new prompt handler with the given name
 func (s *MCPServer) AddPrompt(prompt mcp.Prompt, handler PromptHandlerFunc) {
 	if s.capabilities.prompts == nil {
-		panic("Prompt capabilities not enabled")
+		s.capabilities.prompts = &promptCapabilities{}
 	}
 	s.mu.Lock()
 	defer s.mu.Unlock()
@@ -468,6 +480,9 @@ func (s *MCPServer) AddTool(tool mcp.Tool, handler ToolHandlerFunc) {
 
 // AddTools registers multiple tools at once
 func (s *MCPServer) AddTools(tools ...ServerTool) {
+	if s.capabilities.tools == nil {
+		s.capabilities.tools = &toolCapabilities{}
+	}
 	s.mu.Lock()
 	for _, entry := range tools {
 		s.tools[entry.Tool.Name] = entry
@@ -525,24 +540,33 @@ func (s *MCPServer) handleInitialize(
 ) mcp.JSONRPCMessage {
 	capabilities := mcp.ServerCapabilities{}
 
-	capabilities.Resources = &struct {
-		Subscribe   bool `json:"subscribe,omitempty"`
-		ListChanged bool `json:"listChanged,omitempty"`
-	}{
-		Subscribe:   s.capabilities.resources.subscribe,
-		ListChanged: s.capabilities.resources.listChanged,
+	// Only add resource capabilities if they're configured
+	if s.capabilities.resources != nil {
+		capabilities.Resources = &struct {
+			Subscribe   bool `json:"subscribe,omitempty"`
+			ListChanged bool `json:"listChanged,omitempty"`
+		}{
+			Subscribe:   s.capabilities.resources.subscribe,
+			ListChanged: s.capabilities.resources.listChanged,
+		}
 	}
 
-	capabilities.Prompts = &struct {
-		ListChanged bool `json:"listChanged,omitempty"`
-	}{
-		ListChanged: s.capabilities.prompts.listChanged,
+	// Only add prompt capabilities if they're configured
+	if s.capabilities.prompts != nil {
+		capabilities.Prompts = &struct {
+			ListChanged bool `json:"listChanged,omitempty"`
+		}{
+			ListChanged: s.capabilities.prompts.listChanged,
+		}
 	}
 
-	capabilities.Tools = &struct {
-		ListChanged bool `json:"listChanged,omitempty"`
-	}{
-		ListChanged: s.capabilities.tools.listChanged,
+	// Only add tool capabilities if they're configured
+	if s.capabilities.tools != nil {
+		capabilities.Tools = &struct {
+			ListChanged bool `json:"listChanged,omitempty"`
+		}{
+			ListChanged: s.capabilities.tools.listChanged,
+		}
 	}
 
 	if s.capabilities.logging {

server/server_test.go

@@ -40,13 +40,9 @@ func TestMCPServer_Capabilities(t *testing.T) {
 				)
 				assert.Equal(t, "test-server", initResult.ServerInfo.Name)
 				assert.Equal(t, "1.0.0", initResult.ServerInfo.Version)
-				assert.NotNil(t, initResult.Capabilities.Resources)
-				assert.False(t, initResult.Capabilities.Resources.Subscribe)
-				assert.False(t, initResult.Capabilities.Resources.ListChanged)
-				assert.NotNil(t, initResult.Capabilities.Prompts)
-				assert.False(t, initResult.Capabilities.Prompts.ListChanged)
-				assert.NotNil(t, initResult.Capabilities.Tools)
-				assert.False(t, initResult.Capabilities.Tools.ListChanged)
+				assert.Nil(t, initResult.Capabilities.Resources)
+				assert.Nil(t, initResult.Capabilities.Prompts)
+				assert.Nil(t, initResult.Capabilities.Tools)
 				assert.Nil(t, initResult.Capabilities.Logging)
 			},
 		},
@@ -118,8 +114,8 @@ func TestMCPServer_Capabilities(t *testing.T) {
 				assert.NotNil(t, initResult.Capabilities.Prompts)
 				assert.True(t, initResult.Capabilities.Prompts.ListChanged)
 
-				assert.NotNil(t, initResult.Capabilities.Tools)
-				assert.False(t, initResult.Capabilities.Tools.ListChanged)
+				// Tools capability should be nil when WithToolCapabilities(false) is used
+				assert.Nil(t, initResult.Capabilities.Tools)
 
 				assert.NotNil(t, initResult.Capabilities.Logging)
 			},
@@ -210,7 +206,15 @@ func TestMCPServer_Tools(t *testing.T) {
 				assert.Equal(t, "notifications/tools/list_changed", notifications[0].Notification.Method)
 				// One for DeleteTools
 				assert.Equal(t, "notifications/tools/list_changed", notifications[1].Notification.Method)
-				assert.Equal(t, "Tools not supported", toolsList.(mcp.JSONRPCError).Error.Message)
+				
+				// Expect a successful response with an empty list of tools
+				resp, ok := toolsList.(mcp.JSONRPCResponse)
+				assert.True(t, ok, "Expected JSONRPCResponse, got %T", toolsList)
+				
+				result, ok := resp.Result.(mcp.ListToolsResult)
+				assert.True(t, ok, "Expected ListToolsResult, got %T", resp.Result)
+				
+				assert.Empty(t, result.Tools, "Expected empty tools list")
 			},
 		},
 	}