Sends up to 100 independent SMS messages in one request. Each item is a complete send request with its own recipient, content, id, status, and cost. For a single message, use [Send an SMS message](/docs/api/reference/create-sms-message) instead. Acceptance is all-or-nothing: every item is validated before any is queued, and one invalid item rejects the whole batch with a `422` (nothing is sent). A batch from a workspace with no wallet balance fails with a `402`. The `202` response lists the accepted messages in submission order; each delivers asynchronously and is tracked individually, like a single send. Recipient phone number in E.164 format (for example `+15551234567`). One recipient per message. Sender to send from: an E.164 number (`+15557654321`), an alphanumeric sender ID (1-11 letters, digits, or spaces, for example `MyBrand`), or a short code (5-6 digits). A numeric sender must be a number your workspace owns; an alphanumeric sender is accepted where the destination country permits one. Required on a free-text send: omitting it returns a `422` `SMSNoEligibleSender`. Not accepted alongside `template`, which selects its sender automatically. Free-text message body. Required unless `template` is supplied (the two are mutually exclusive). At least 1 character, up to a 12-segment cap (roughly 1836 GSM-7 or 804 UCS-2 characters). Bird does not truncate; a body exceeding 12 segments is rejected with a 422. The limit is on segment count, not characters, because GSM-7 and UCS-2 encodings differ in characters per segment. Content classification. Tells Bird and carriers why you're sending; per-country compliance rules (opt-out policy, quiet hours) key on it as they roll out. Required on a free-text send; omit it on a template send, where the category is derived from the template. Preview feature: how long, in seconds (60-172800), Bird keeps trying to deliver before the message transitions to `expired`. Currently unavailable; supplying this field returns `422 SMSUnsupportedFeature`. Structured `{name, value}` labels for filtering and analytics. Tags become first-class query dimensions: filter the list endpoint by tag name, slice analytics by tag, and surface in webhook payloads. Maximum 20 tags per send. Use tags for low-cardinality dimensions (`category`, `experiment_variant`). For arbitrary structured context you do not need as a filter dimension, use `metadata` instead. Tag name. ASCII letters, digits, underscore, and hyphen only. Case-sensitive. Maximum 32 characters. Tag value. ASCII letters, digits, underscore, and hyphen only. Case-sensitive. Maximum 64 characters. Arbitrary JSON object stored on the message, returned on API reads, and echoed in webhook payloads. Maximum 2 KB serialized. Use metadata for per-send context like internal IDs and foreign keys. For low-cardinality filterable labels, use `tags` instead. Preview feature: multimedia (MMS) attachments. Currently unavailable; supplying this field returns `422 SMSUnsupportedFeature`. Preview feature: sender selection from a messaging profile pool. Currently unavailable; supplying this field returns `422 SMSUnsupportedFeature`. Preview feature: send-later scheduling. Currently unavailable; supplying this field returns `422 SMSUnsupportedFeature`. Send using a stored template instead of free text. Mutually exclusive with `text`; the message category is derived from the template, so `from`, `category`, and `media_urls` are not accepted alongside it. The template to send, by its id. The template to send, by its name handle (for example `bird_otp_verification`). Browse the available templates and their variables with the templates endpoint. Language tag (BCP 47, for example `fr` or `pt-BR`) selecting the localized body. Falls back to the closest available language, then English, when the exact tag is not stocked. Omit for English. Values for the template's variables, keyed by variable name. The accepted keys and their formats are fixed per template (the template's `variables` on the templates endpoint). A missing required variable, an undeclared key, a value that does not match its variable's format, or a serialized payload over 16 KB each return a `422`. Preview feature: broadcast correlation. Currently unavailable; supplying this field returns `422 SMSUnsupportedFeature`. Preview feature: campaign correlation for analytics. Currently unavailable; supplying this field returns `422 SMSUnsupportedFeature`. Preview feature: audience-targeted sends. Currently unavailable; supplying this field returns `422 SMSUnsupportedFeature`. Preview feature: contact-targeted sends. Currently unavailable; supplying this field returns `422 SMSUnsupportedFeature`. Preview feature: topic-gated sends. Currently unavailable; supplying this field returns `422 SMSUnsupportedFeature`. Preview feature: per-segment price ceiling. Currently unavailable; supplying this field returns `422 SMSUnsupportedFeature`. Preview feature: per-recipient substitution for batch sends. Currently unavailable; supplying this field returns `422 SMSUnsupportedFeature`. Preview feature: link click tracking. Defaults to `false`. Currently unavailable; setting this to `true` returns `422 SMSUnsupportedFeature`. One entry per message in the batch, in submission order. ID of the message (`sms_`-prefixed), assigned when the send is accepted. Pass it as `message_id` to the get-message endpoint. Whether the message was sent from a Bird sender (`outbound`) or received from a subscriber (`inbound`). Possible values: `outbound`, `inbound` Recipient phone number in E.164 format. Sender the message was sent from: an E.164 number, an alphanumeric sender ID, or a short code. The message body as sent. For a template send, this is the rendered text after parameter substitution. Content classification supplied on the send. Null for inbound messages. Segment breakdown for the body. Number of segments the body is split into. Each segment is a billable unit. Encoding used for the body. `GSM_7BIT` fits 160 characters in a single segment (153 per part when multi-segment); `UCS2` is used when the body contains any character outside the GSM 03.38 alphabet (emoji, CJK, some accented characters) and fits 70 characters in a single segment (67 per part when multi-segment). Possible values: `GSM_7BIT`, `UCS2` Character count of the body under the selected encoding. Cost of the message. Null until the message has been priced. ISO 4217 currency code for the cost amount. Omitted when the cost is not denominated in a currency (for example a zero-priced internal send). Total cost as a decimal string: the per-segment rate multiplied by the segment count, plus any surcharges. Per-component cost breakdown. Returned on single-message reads; omitted from list rows. Per-segment price as a decimal string. Number of billable segments. ISO 3166-1 alpha-2 destination country the price was resolved for. Carrier surcharge component as a decimal string (for example US 10DLC fees). `0.0000` when none applies. Structured `{name, value}` filter labels applied to this message. Tag name. ASCII letters, digits, underscore, and hyphen only. Case-sensitive. Maximum 32 characters. Tag value. ASCII letters, digits, underscore, and hyphen only. Case-sensitive. Maximum 64 characters. Arbitrary JSON metadata stored on the message and echoed in webhook payloads. How long, in seconds, Bird keeps trying to deliver before the message transitions to `expired`. Carrier that handled the message, when known. Populated once a delivery receipt identifies it. Mobile country code and mobile network code of the carrier, when known. Failure detail on a terminally failed or rejected message. Present only when the message failed. Bird-stable failure reason. `invalid_destination`: the number is not assigned, ported out, or malformed. `unreachable`: handset off or out of coverage. `blocked_by_carrier`: the carrier filtered the message. `blocked_by_recipient`: the recipient device blocked the sender. `landline_unreachable`: the destination is a landline that does not accept SMS. `content_rejected`: the carrier rejected the content. `sender_unregistered`: the sender is not registered for the destination. `recipient_opted_out`: the recipient is on a suppression list. `provider_unavailable`: an upstream failure after retries. `insufficient_balance`: the workspace wallet had insufficient balance to send the message. `unknown`: an unmapped failure. Possible values: `invalid_destination`, `unreachable`, `blocked_by_carrier`, `blocked_by_recipient`, `landline_unreachable`, `content_rejected`, `sender_unregistered`, `recipient_opted_out`, `provider_unavailable`, `insufficient_balance`, `unknown` Human-readable explanation of the failure. Raw carrier-supplied error code, when available, for low-level debugging. When the failure occurred. When the message was accepted (outbound) or received (inbound). When the message was handed to the carrier. Null until then. When delivery was confirmed. Null until then. Aggregate result for the batch. Number of messages accepted in the batch. Acceptance is all-or-nothing, so this equals the number of messages submitted.