Vertex AI MCP Server

Instructions

Implementation Reference

• src/index.ts:464-473 (handler)

  Handler logic for 'list_directory_contents' tool: parses args, validates path, reads directory entries using fs.readdir, formats output with [DIR]/[FILE] prefixes, sorts and joins.

  case "list_directory_contents": {
    const parsed = ListDirectoryArgsSchema.parse(args);
    const validPath = validateWorkspacePath(parsed.path);
    const entries = await fs.readdir(validPath, { withFileTypes: true });
    resultText = entries
      .map((entry) => `${entry.isDirectory() ? "[DIR] " : "[FILE]"} ${entry.name}`)
      .sort()
      .join("\n");
     if (!resultText) resultText = "(Directory is empty)";
    break;

• src/tools/list_directory.ts:6-12 (schema)

  Zod schema definition for input arguments (path: string) and conversion to JSON schema used in tool definition.

  // Schema definition (adapted from example.ts) - Exported
  export const ListDirectoryArgsSchema = z.object({
    path: z.string().describe("The path of the directory to list (relative to the workspace directory)."),
  });
  
  // Convert Zod schema to JSON schema
  const ListDirectoryJsonSchema = zodToJsonSchema(ListDirectoryArgsSchema);

• src/tools/index.ts:53-53 (registration)

  Registration of listDirectoryTool in the allTools array, which is exported and used by the MCP server.

  listDirectoryTool,

• src/tools/index.ts:13-13 (registration)

  Import of the listDirectoryTool for inclusion in allTools.

  import { listDirectoryTool } from "./list_directory.js";

• src/tools/list_directory.ts:14-37 (schema)

  Full tool definition including name, description, inputSchema reference, and buildPrompt for validation.

  export const listDirectoryTool: ToolDefinition = {
      name: "list_directory_contents", // Renamed slightly
      description:
        "Get a detailed listing of all files and directories directly within a specified path in the workspace filesystem. " +
        "Results clearly distinguish between files and directories with [FILE] and [DIR] " +
        "prefixes. This tool is essential for understanding directory structure and " +
        "finding specific files within a directory. Does not list recursively.",
      inputSchema: ListDirectoryJsonSchema as any, // Cast as any if needed
  
      // Minimal buildPrompt as execution logic is separate
      buildPrompt: (args: any, modelId: string) => {
          const parsed = ListDirectoryArgsSchema.safeParse(args);
          if (!parsed.success) {
              throw new McpError(ErrorCode.InvalidParams, `Invalid arguments for list_directory_contents: ${parsed.error}`);
          }
          return {
              systemInstructionText: "",
              userQueryText: "",
              useWebSearch: false,
              enableFunctionCalling: false
          };
      },
      // No 'execute' function here
  };