Give a CrewAI Agent a Code Interpreter That Runs in a MicroVM

python3.12 -m venv venv && . venv/bin/activate
pip install crewai sandboxer-sdk
export SANDBOXER_API_KEY=sbx_live_…

import shlex
import uuid
from typing import List, Optional, Type

from crewai.tools import BaseTool
from pydantic import BaseModel, Field, PrivateAttr
from sandboxer import Sandbox, Sandboxer


class RunPythonInput(BaseModel):
    code: str = Field(..., description="Python 3 code to run. Print what you want to see.")
    libraries_used: List[str] = Field(
        default_factory=list,
        description="PyPI packages the code needs, installed with pip before it runs.",
    )


class SandboxerCodeInterpreterTool(BaseTool):
    name: str = "sandboxer_code_interpreter"
    description: str = (
        "Runs Python 3 code in an isolated cloud microVM (Ubuntu). "
        "Files and installed packages persist between calls. Returns exit code, stdout and stderr."
    )
    args_schema: Type[BaseModel] = RunPythonInput

    sandbox_name: str = "crewai-code"
    sandbox_type: str = "small"
    ttl_seconds: int = 1800
    timeout_seconds: int = 300

    _client: Optional[Sandboxer] = PrivateAttr(default=None)
    _sandbox: Optional[Sandbox] = PrivateAttr(default=None)

    def _get_sandbox(self) -> Sandbox:
        if self._sandbox is None:
            self._client = Sandboxer()  # reads SANDBOXER_API_KEY
            self._sandbox = self._client.create(
                type=self.sandbox_type, ttl_seconds=self.ttl_seconds, name=self.sandbox_name
            )  # waits until ready
        return self._sandbox

    def _run(self, code: str, libraries_used: Optional[List[str]] = None) -> str:
        sandbox = self._get_sandbox()
        if libraries_used:
            pkgs = " ".join(shlex.quote(p) for p in libraries_used)
            install = sandbox.exec(
                f"pip install -q --break-system-packages {pkgs}", timeout_seconds=self.timeout_seconds
            )
            if install.exit_code != 0:
                return f"pip install failed (exit {install.exit_code})\n{install.stderr[-2000:]}"
        path = f"crewai/{uuid.uuid4().hex[:8]}.py"
        sandbox.files.write(path, code)
        result = sandbox.exec(["python3", path], timeout_seconds=self.timeout_seconds)
        out = f"exit code {result.exit_code}\n{result.stdout}"
        if result.stderr:
            out += f"\nstderr:\n{result.stderr}"
        return out[-8000:]

    def close(self, delete: bool = False) -> None:
        if self._sandbox is not None:
            self._sandbox.delete() if delete else self._sandbox.stop()
            self._sandbox = None

tool = SandboxerCodeInterpreterTool()
try:
    print(tool._run(code="import platform, os\nprint(platform.platform())\nprint('user', os.getuid())\nopen('notes.txt','w').write('42')"))
    print(tool.run(code="import os, humanize\nprint(open('notes.txt').read())\nprint(humanize.naturalsize(os.path.getsize('/usr/bin/python3')))", libraries_used=["humanize"]))
    print(tool.run(code="1/0"))
finally:
    tool.close(delete=True)

exit code 0
Linux-6.18.56-sandboxer-x86_64-with-glibc2.39
user 1000

exit code 0
42
8.0 MB

exit code 1

stderr:
Traceback (most recent call last):
  File "/home/user/crewai/e1650c80.py", line 1, in <module>
    1/0
    ~^~
ZeroDivisionError: division by zero