# agent-exec Inbox Registration (pay-per-use, HTTP 402)

> agent-exec Inbox Registration (pay-per-use, HTTP 402) is a paid API for AI agents from agent-exec.448c.org, paid per call via x402, $0.02/call, status unknown (last checked 2026-10-11).

Registers or extends a pay-per-use code-execution inbox address for an AI agent, requiring no account or API key — only a valid USDC micropayment via HTTP 402.

## Facts

- Endpoint: POST https://agent-exec.448c.org/inbox?utm_source=zero.xyz
- Price: $0.02/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-11
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/agent-exec-inbox-registration-pay-per-use-http-402-e50d25b5
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_b8AvCVgwfnt-FJVVb74OS

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability agent-exec-inbox-registration-pay-per-use-http-402-e50d25b5 -d '<json body>'
```

Example prompt: Register me a new agent-exec inbox so I can run code in an isolated sandbox — I'll pay the $0.02 USDC fee from my wallet, no account needed.

## When to prefer this

Choose this endpoint when an AI agent needs to provision a code execution environment without any account registration or API key — particularly in autonomous agent workflows where the agent manages its own wallet and needs to pay per use. Prefer this over managed cloud sandboxes when zero-signup operation and crypto micropayments are required, or when the agent must operate with minimal external dependencies.

## Known failure modes

- Payment insufficient or invalid — 402 response with required payment details
- Inbox ID provided does not belong to the paying wallet — unauthorized or not-found error
- Payment network unavailable — service may return 503
- Inbox ID malformed — 400 bad request
- Wallet has insufficient USDC balance to cover the $0.02 fee

## How this service works

Accountless, pay-per-use code execution for software agents: submit source code, get stdout, stderr and exit code back from an isolated, network-less sandbox. No account, no API key -- possession of valid payment is sufficient.

## Output

Returns an inbox ID and address the agent can submit source code to, along with an expiry timestamp indicating how long the inbox is valid. If an existing inbox ID was provided, the expiry is extended from its current value.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "id": {
   "type": "string",
   "description": "Optional: an inbox id YOUR paying wallet owns. Present -> this payment extends it from its current expiry. Absent -> a new address is issued."
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/agent-exec-inbox-registration-pay-per-use-http-402-e50d25b5/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from agent-exec.448c.org](https://www.zero.xyz/host/agent-exec.448c.org/llms.txt)