# Machine Inbox — Extend Inbox

> Machine Inbox — Extend Inbox is a paid API for AI agents from machineinbox.com, paid per call via x402, $1/call, status unknown (last checked 2026-09-10).

Extends an existing Machine Inbox email inbox by 7 days for $1 USDC via x402.

## Facts

- Endpoint: POST https://machineinbox.com/api/v1/inboxes/%7BinboxId%7D/extend
- Price: $1/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-10
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/machine-inbox-extend-inbox-883116a1
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_zMOP-jCOqcQWJH_NQG_24

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 machine-inbox-extend-inbox-883116a1 -d '<json body>'
```

Example prompt: My Machine Inbox inbox abc-1234-uuid is about to expire — extend it by 7 more days using $1 USDC.

## When to prefer this

Use this endpoint when an existing Machine Inbox inbox is approaching its expiration and needs to be kept alive for another 7 days. Prefer this over creating a new inbox when continuity of the same email address matters (e.g., ongoing correspondence, agent pipelines waiting on replies). This is the right choice if you already have an inboxId and simply want to extend its lifetime rather than provision a fresh inbox.

## Known failure modes

- Inbox ID not found — returns error if inboxId is invalid or doesn't exist
- Payment failure — x402 USDC payment of $1 not received or rejected
- Inbox already expired — cannot extend an inbox that is no longer active
- Duplicate extension attempt in quick succession — may not be idempotent, could double-charge

## How this service works

Pay-per-use email inboxes for software agents. Pay $2.00 through Stripe Machine Payments Protocol or x402 USDC, receive mail, and reply over HTTP.

## Output

Returns a JSON object confirming the extension was applied (applied: true), along with the extension details including the number of days added (7), the inboxId, and the new expiration timestamp in ISO 8601 format.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method",
    "bodyType",
    "body"
   ],
   "properties": {
    "body": {
     "type": "object",
     "additionalProperties": false
    },
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "POST",
      "PUT",
      "PATCH"
     ],
     "type": "string"
    },
    "bodyType": {
     "enum": [
      "json",
      "form-data",
      "text"
     ],
     "type": "string"
    },
    "pathParams": {
     "type": "object",
     "required": [
      "inboxId"
     ],
     "properties": {
      "inboxId": {
       "type": "string",
       "format": "uuid"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "applied": true,
  "extension": {
   "days": 7,
   "inboxId": "uuid",
   "expiresAt": "2026-09-01T12:00:00.000Z"
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/machine-inbox-extend-inbox-883116a1/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from machineinbox.com](https://www.zero.xyz/host/machineinbox.com/llms.txt)