# Simulate an inbound SMS (test keys only)

Source: https://joinsimplesms.com/docs/api/test/simulate-inbound
Index: https://joinsimplesms.com/llms.txt

`POST /v1/test/inbound`

Send your API key as a bearer token: `Authorization: Bearer ssms_sk_...`. Test keys run this endpoint against the [sandbox](/docs/sandbox); see [Authentication](/docs/authentication) for key modes and scopes.

## Request body

JSON (`Content-Type: application/json`).

| Field | Type | Required | Description |
| --- | --- | --- | --- |
| `to` | string | Yes | One of your sandbox numbers |
| `from` | string | Yes |  |
| `body` | string | Yes |  |

## Responses

| Status | Meaning | Body |
| --- | --- | --- |
| 201 | Simulated inbound message | `Message` |
| 401 | Missing, malformed, or revoked API key | `Error` |
| 402 | Billable live calls only: the prepaid credit balance cannot cover the call (insufficient_credits); nothing was done or charged | `Error` |
| 403 | Live keys not allowed | `Error` |
| 429 | Rate limit or quota exceeded | `Error` |

### 201: `Message` fields

| Field | Type | Description |
| --- | --- | --- |
| `id` | string | Example: `msg_a1B2c3D4e5F6g7H8`. |
| `object` | `message` |  |
| `to` | string | Example: `+15005550006`. |
| `from` | string | Example: `+15005550100`. |
| `body` | string |  |
| `direction` | `outbound`, `inbound` |  |
| `status` | `queued`, `sent`, `delivered`, `failed`, `received` |  |
| `test` | boolean |  |
| `simulated` | boolean | True when nothing was handed to a carrier: every test-key message except one sent to your own verified phone. Always false on live messages. A simulated message still reaches `delivered`. |
| `notice` | string | Only on the response to POST /messages. Present when a test-key send to a real-looking number was simulated: says nothing was sent and how to send for real. |
| `schedule_id` | string | The recurring schedule this message is an occurrence of. Present only when set. |
| `created_at` | string (date-time) |  |
| `media` | array of string (uri) | MMS attachments (inbound today). |
| `sent_by` | string | Console user or API key that composed it. |
| `failure_reason` | string | The carrier's raw text for a failed send. Kept for compatibility; see `failure`. |
| `attempts` | integer | Live sends: carrier submissions so far. More than 1 means it was retried. |
| `next_attempt_at` | string (date-time) | Present while queued for an automatic carrier retry. |
| `receipt_status` | `missing` | The carrier accepted the message but sent no delivery report within 72 hours. status stays sent. |
| `customer_id` | string | The customer this is attributed to. Present only when set. |
| `timeline` | array of object | Every status transition, oldest first. Inbound messages have a single `received`. |
| `timeline[].status` | `accepted`, `validated`, `queued`, `sent_to_carrier`, `carrier_accepted`, `retry_scheduled`, `delivered`, `failed`, `received` |  |
| `timeline[].at` | string (date-time) |  |
| `timeline[].attempt` | integer | Carrier attempt this step belongs to (from sent_to_carrier on). |
| `segments` | integer | Parts the body is split into (GSM-7: 160, then 153 each; UCS-2: 70, then 67). Example: `1`. |
| `encoding` | `gsm7`, `ucs2` |  |
| `price` | object | What this message costs, in USD. One all-in rate per outbound message; carrier fees are included (a 0 line). Null on messages sent before prices were recorded. Nullable. |
| `price.total` | number | Example: `0.009`. |
| `price.currency` | `usd` |  |
| `price.breakdown` | array of object |  |
| `price.breakdown[].label` | string |  |
| `price.breakdown[].amount` | number |  |
| `destination_carrier` | string | The recipient's mobile carrier, when a cached lookup knows it. Nullable. |
| `failure` | Failure | Null unless status is `failed`. Nullable. |

## Errors

| Status | When |
| --- | --- |
| 401 | Missing, malformed, or revoked API key |
| 402 | Billable live calls only: the prepaid credit balance cannot cover the call (insufficient_credits); nothing was done or charged |
| 403 | Live keys not allowed |
| 429 | Rate limit or quota exceeded |

Every error has the same JSON shape, and `request_id` matches the `X-Request-Id` response header. [Errors](/docs/errors) lists every code and what to do about it.

```json
{
  "error": {
    "code": "invalid_request",
    "message": "What went wrong, in plain words.",
    "param": "the_field",
    "request_id": "req_a1B2c3D4e5F6g7H8"
  }
}
```

## Examples

### curl

```bash
curl -X POST "https://api.joinsimplesms.com/v1/test/inbound" \
  -H "Authorization: Bearer $SIMPLESMS_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
  "to": "+14155550132",
  "from": "+15005550100",
  "body": "Hello from SimpleSMS"
}'
```

### Node.js

The Node.js SDK does not wrap this endpoint yet; call it with `fetch`.

```javascript
const res = await fetch('https://api.joinsimplesms.com/v1/test/inbound', {
  method: 'POST',
  headers: {
    Authorization: `Bearer ${process.env.SIMPLESMS_API_KEY}`,
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
    "to": "+14155550132",
    "from": "+15005550100",
    "body": "Hello from SimpleSMS"
  }),
});

if (!res.ok) throw new Error((await res.json()).error.message);
const data = await res.json();
```

### Python

The Python SDK does not wrap this endpoint yet; call it over HTTP.

```python
import json, os, urllib.request

req = urllib.request.Request(
    "https://api.joinsimplesms.com/v1/test/inbound",
    method="POST",
    headers={
        "Authorization": f"Bearer {os.environ['SIMPLESMS_API_KEY']}",
        "Content-Type": "application/json",
    },
    data=json.dumps({
        "to": "+14155550132",
        "from": "+15005550100",
        "body": "Hello from SimpleSMS"
    }).encode(),
)
with urllib.request.urlopen(req) as res:
    data = json.load(res)
```

## Related

- Guide: [Sandbox & test numbers](/docs/sandbox)
- [All sandbox endpoints](/docs/api#test)
- [API reference](/docs/api)