Node.js Sandbox MCP Server

Instructions

Implementation Reference

• src/tools/exec.ts:11-36 (handler)

  The handler function that executes one or more shell commands inside a running sandbox Docker container using docker exec.

  export default async function execInSandbox({
    container_id,
    commands,
  }: {
    container_id: string;
    commands: string[];
  }): Promise<McpResponse> {
    if (!isDockerRunning()) {
      return {
        content: [textContent(DOCKER_NOT_RUNNING_ERROR)],
      };
    }
  
    const output: string[] = [];
    for (const cmd of commands) {
      output.push(
        execSync(
          `docker exec ${container_id} /bin/sh -c ${JSON.stringify(cmd)}`,
          {
            encoding: 'utf8',
          }
        )
      );
    }
    return { content: [textContent(output.join('\n'))] };
  }

• src/tools/exec.ts:6-9 (schema)

  Zod schema for input validation: container_id (string) and commands (array of non-empty strings).

  export const argSchema = {
    container_id: z.string(),
    commands: z.array(z.string().min(1)),
  };

• src/server.ts:58-63 (registration)

  Registers the sandbox_exec tool with the MCP server, providing name, description, schema (execSchema), and handler (execInSandbox).

  server.tool(
    'sandbox_exec',
    'Execute one or more shell commands inside a running sandbox container. Requires a sandbox initialized beforehand.',
    execSchema,
    execInSandbox
  );