fix(mcp): add readonly guard to createHandler

pkg/mcp/instructions_warning.md

@@ -7,20 +7,20 @@
 The Functions MCP server is currently running in **read-only mode**.
 
 **Available operations:**
-- Create Functions
-- Build Functions
 - Configure Functions (envs, labels, volumes)
 - Inspect Functions
 
 **Disabled operations:**
+- Create Functions
+- Build Function images
 - Deploy to cluster
 - Delete from cluster
 
-These write operations are disabled to prevent unintended cluster modifications.
+These write operations are disabled to prevent unintended local or cluster modifications.
 
 ## Enabling Write Mode
 
-If the user needs to deploy or delete Functions, you MUST inform them to enable write mode:
+If the user needs to create, build, deploy, or delete Functions, you MUST inform them to enable write mode:
 
 1. Close/exit this application completely
 2. Set the environment variable: `FUNC_ENABLE_MCP_WRITE=true`

pkg/mcp/tools_create.go

@@ -20,6 +20,10 @@ var createTool = &mcp.Tool{
 }
 
 func (s *Server) createHandler(ctx context.Context, r *mcp.CallToolRequest, input CreateInput) (result *mcp.CallToolResult, output CreateOutput, err error) {
+	if s.readonly.Load() {
+		err = fmt.Errorf("the server is currently in read-only mode; to enable write operations, set FUNC_ENABLE_MCP_WRITE in the server environment and restart the server")
+		return
+	}
 	out, err := s.executor.Execute(ctx, "create", input.Args()...)
 	if err != nil {
 		err = fmt.Errorf("%w\n%s", err, string(out))

pkg/mcp/tools_create_test.go

@@ -123,3 +123,25 @@ func TestTool_Create_BinaryFailure(t *testing.T) {
 		t.Errorf("expected error to include binary output, got: %s", resultToString(result))
 	}
 }
+
+// TestTool_Create_Readonly ensures the create tool rejects requests in readonly mode.
+func TestTool_Create_Readonly(t *testing.T) {
+	client, _, err := newTestPairWithReadonly(t, true) // readonly = true
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	result, err := client.CallTool(t.Context(), &mcp.CallToolParams{
+		Name:      "create",
+		Arguments: map[string]any{"language": "go", "path": "."},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !result.IsError {
+		t.Fatal("expected create to be rejected in readonly mode")
+	}
+	if !strings.Contains(resultToString(result), "read-only mode") {
+		t.Errorf("expected readonly error message, got: %s", resultToString(result))
+	}
+}