Code Mode - mcp-use

Code mode exposes execute_code and search_tools so agents run JavaScript with access to connected MCP tools instead of making individual tool calls. Node.js only.

Enable

import { mkdir } from "node:fs/promises";
import { resolve } from "node:path";
import { MCPClient } from "@mcp-use/client";

const directory = resolve("./data");
await mkdir(directory, { recursive: true });

const client = new MCPClient(
  {
    mcpServers: {
      fs: {
        command: "npx",
        args: ["-y", "@modelcontextprotocol/server-filesystem", directory],
      },
    },
  },
  { codeMode: true },
);

try {
  const result = await client.executeCode(`
    return await fs.list_directory({ path: ${JSON.stringify(directory)} });
  `);

  console.log(result.result, result.logs, result.error);
} finally {
  await client.close();
}

The filesystem server’s list_directory tool returns a formatted string, so result.result contains the directory listing. A string’s .length counts characters, not directory entries. The example creates ./data if needed and uses its absolute path for both the server’s allowed directory and the tool call.

Executors

Executor	Use case
`"vm"` (default)	Local Node.js VM — fast, trusted environments
`"e2b"`	Cloud sandbox — untrusted code (`@e2b/code-interpreter` + API key)
Custom function / `BaseCodeExecutor`	Your own runtime

{ codeMode: {
    enabled: true,
    executor: "e2b",
    executorOptions: { apiKey: process.env.E2B_API_KEY!, timeoutMs: 300_000 },
}}

A custom function receives (code, timeout?) and returns an ExecutionResult. It owns cleanup for whatever runtime it wraps — client.close() does not release anything on its behalf. A non-arrow function is invoked with the MCPClient as its this, so it can reach the client without closing over it:

{ codeMode: {
    enabled: true,
    executor: async function (this: MCPClient, code, timeout) {
      const servers = this.getServerNames();
      return {
        result: await myRuntime.run(code, timeout, servers),
        logs: [],
        error: null,
        execution_time: 0,
      };
    },
}}

Agent integration

Use with @mcp-use/agent and PROMPTS.CODE_MODE:

import { MCPAgent, PROMPTS } from "@mcp-use/agent";

const agent = new MCPAgent({ llm, client, systemPrompt: PROMPTS.CODE_MODE });
await agent.run("List all files and count them");

Reference

Client API reference — config types, searchTools, and ExecutionResult. Anthropic: Code execution with MCP

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