# Capability

## Check iMessage capability

`client.capability.checkIMessage(CapabilityCheckIMessageParamsbody, RequestOptionsoptions?): HandleCheckResponse`

**post** `/v3/capability/check_imessage`

Check whether a recipient address (phone number or email) is reachable via iMessage.

### Parameters

- `body: CapabilityCheckIMessageParams`

  - `address: string`

    The recipient address to check. `check_imessage` accepts an E.164 phone number or an
    email address; `check_rcs` accepts an E.164 phone number only and rejects an email
    with a `400`, since RCS has no email addressing.

  - `from?: string`

    Optional sender phone number. If omitted, an available phone from your pool is used automatically.

### Returns

- `HandleCheckResponse`

  - `address: string`

    The recipient address that was checked

  - `available: boolean`

    Whether the recipient supports the checked messaging service

  - `reason?: "not_supported"`

    Why `available` is `false`. Only present on a negative result.

    `not_supported` is the only value returned with a `200`, and it means the check
    completed and the recipient is genuinely not reachable over this service. On
    `check_rcs`, sender-side faults do not return `200` — they return `503` with a
    specific error code. `check_imessage` does not use this mapping.

    - `"not_supported"`

  - `selected_service?: string`

    The service that would actually carry a message to this address right now, which is
    not always the service you checked — a recipient without RCS resolves to `SMS`.
    Absent when the check could not determine one.

### Example

```typescript
import LinqAPIV3 from '@linqapp/sdk';

const client = new LinqAPIV3({
  apiKey: process.env['LINQ_API_V3_API_KEY'], // This is the default and can be omitted
});

const handleCheckResponse = await client.capability.checkIMessage({ address: '+15551234567' });

console.log(handleCheckResponse.address);
```

#### Response

```json
{
  "address": "+15551234567",
  "available": true
}
```

## Check RCS capability

`client.capability.checkRCS(CapabilityCheckRCSParamsbody, RequestOptionsoptions?): HandleCheckResponse`

**post** `/v3/capability/check_rcs`

Check whether a recipient address (phone number) supports RCS messaging.

`address` must be an E.164 phone number. RCS has no email addressing, so an email is
rejected with a `400` rather than attempted.

A `200` means the check ran and the answer is about the **recipient**. A `503` means the
check could not produce an answer because of a fault on the **sender** line — `4004`
(RCS not turned on for the line), `4009` (line has no RCS account), or `4010` (the check
could not run). Treat all three as "unknown", never as "the recipient does not support
RCS", and do not cache them as a negative result.

### Parameters

- `body: CapabilityCheckRCSParams`

  - `address: string`

    The recipient address to check. `check_imessage` accepts an E.164 phone number or an
    email address; `check_rcs` accepts an E.164 phone number only and rejects an email
    with a `400`, since RCS has no email addressing.

  - `from?: string`

    Optional sender phone number. If omitted, an available phone from your pool is used automatically.

### Returns

- `HandleCheckResponse`

  - `address: string`

    The recipient address that was checked

  - `available: boolean`

    Whether the recipient supports the checked messaging service

  - `reason?: "not_supported"`

    Why `available` is `false`. Only present on a negative result.

    `not_supported` is the only value returned with a `200`, and it means the check
    completed and the recipient is genuinely not reachable over this service. On
    `check_rcs`, sender-side faults do not return `200` — they return `503` with a
    specific error code. `check_imessage` does not use this mapping.

    - `"not_supported"`

  - `selected_service?: string`

    The service that would actually carry a message to this address right now, which is
    not always the service you checked — a recipient without RCS resolves to `SMS`.
    Absent when the check could not determine one.

### Example

```typescript
import LinqAPIV3 from '@linqapp/sdk';

const client = new LinqAPIV3({
  apiKey: process.env['LINQ_API_V3_API_KEY'], // This is the default and can be omitted
});

const handleCheckResponse = await client.capability.checkRCS({ address: '+15551234567' });

console.log(handleCheckResponse.address);
```

#### Response

```json
{
  "address": "+15551234567",
  "available": true
}
```

## Domain Types

### Handle Check

- `HandleCheck`

  - `address: string`

    The recipient address to check. `check_imessage` accepts an E.164 phone number or an
    email address; `check_rcs` accepts an E.164 phone number only and rejects an email
    with a `400`, since RCS has no email addressing.

  - `from?: string`

    Optional sender phone number. If omitted, an available phone from your pool is used automatically.

### Handle Check Response

- `HandleCheckResponse`

  - `address: string`

    The recipient address that was checked

  - `available: boolean`

    Whether the recipient supports the checked messaging service

  - `reason?: "not_supported"`

    Why `available` is `false`. Only present on a negative result.

    `not_supported` is the only value returned with a `200`, and it means the check
    completed and the recipient is genuinely not reachable over this service. On
    `check_rcs`, sender-side faults do not return `200` — they return `503` with a
    specific error code. `check_imessage` does not use this mapping.

    - `"not_supported"`

  - `selected_service?: string`

    The service that would actually carry a message to this address right now, which is
    not always the service you checked — a recipient without RCS resolves to `SMS`.
    Absent when the check could not determine one.