Code Execution

Code Execution Sandbox

Two tiers of sandboxed code execution, paywalled via x402. An agent sends source code and gets back stdout, stderr, and the expression result -- all executed in an isolated cloud VM via E2B. No API key needed on the caller's side, no signup, no account. The operator's own E2B_API_KEY handles upstream auth; per-tier timeout and code-size caps bound compute cost.

Tiers

Endpoint	Price	Timeout	Code cap	Languages
POST /api/code-run	$0.02	30s	10,000 chars	Python, JavaScript
POST /api/code-run-pro	$0.05	60s	50,000 chars	Python, JavaScript

Both tiers are wallet-only -- there is no proof-of-work free tier because every call spins up a real cloud VM. See Security Model for the wallet-only rationale.

Request format

Both tiers accept the same JSON body:

{
  "code": "print('Hello from Agent402!')",
  "language": "python"
}

Field	Required	Notes
code	yes	Source code to execute; max length varies by tier
language	no	python (default) or javascript

Response format

Both tiers return the same envelope:

{
  "language": "python",
  "stdout": "Hello from Agent402!\n",
  "stderr": "",
  "result": null,
  "error": null
}

Field	Description
language	The language the code was executed in
stdout	Standard output from the execution
stderr	Standard error from the execution
result	The value of the last expression (if any)
error	Error details if the code failed, or null

Error shape

When code raises an exception, the error field contains:

{
  "error": {
    "name": "NameError",
    "message": "name 'x' is not defined",
    "traceback": "Traceback (most recent call last):\n  ..."
  }
}

Curl examples

Standard tier ($0.02 -- Python, 30s)

curl -X POST https://agent402.tools/api/code-run \
  -H 'Content-Type: application/json' \
  -d '{
    "code": "import math\nprint(f\"Pi is approximately {math.pi:.10f}\")\nmath.factorial(20)",
    "language": "python"
  }'

Standard tier -- JavaScript

curl -X POST https://agent402.tools/api/code-run \
  -H 'Content-Type: application/json' \
  -d '{
    "code": "const fib = n => n <= 1 ? n : fib(n-1) + fib(n-2); console.log(fib(10)); 55",
    "language": "javascript"
  }'

Pro tier ($0.05 -- longer computations, 60s)

curl -X POST https://agent402.tools/api/code-run-pro \
  -H 'Content-Type: application/json' \
  -d '{
    "code": "import numpy as np\narr = np.random.randn(1000000)\nprint(f\"mean={arr.mean():.4f}, std={arr.std():.4f}\")\narr.shape",
    "language": "python"
  }'

All endpoints return 402 without a valid x402 payment header -- the same flow as every other paid tool. See Paying with x402 for how to sign and attach payment.

Security model

Each call runs in a fully isolated E2B sandbox (ephemeral cloud VM):

• No access to the Agent402 server's filesystem, network, or secrets
• No state persists between callers -- the VM is destroyed after each execution
• Timeout enforcement prevents infinite loops from burning compute
• Code size cap prevents payload abuse
• The E2B_API_KEY is read at call time and never exposed in responses or error messages

Environment gating

The kit lazy-loads the E2B SDK and reads E2B_API_KEY at call time, not at boot. If the key is missing or empty, calls return 503 Service Unavailable and the rest of the server continues running normally. Self-hosters who don't want to offer code execution simply omit the env var -- no code change needed.

See also

• LLM Proxy Gateway -- text inference proxy
• Image Generation Gateway -- image generation proxy
• Paying with x402 -- the USDC payment flow these endpoints require
• Security Model -- why these tools are wallet-only (no PoW free tier)
• Tool Catalog -- where these tools sit in the catalog