# Send a message

You can send a message from a Conversation app to a contact associated with that app. If the recipient is not associated with an existing contact, a new contact will be created.
The message is added to the active conversation with the contact if a conversation already exists. If no active conversation exists a new one is started automatically.
You can find all of your IDs and authentication credentials on the [Sinch Customer Dashboard](https://dashboard.sinch.com/settings/access-keys).

Endpoint: POST /v1/projects/{project_id}/messages:send
Version: 1.0
Security: Basic, oAuth2

## Security:

  - `Basic` (unknown)
    http basic

  - `oAuth2` (unknown)
    oauth2

## Path parameters:

  - `project_id` (string, required)
    The unique ID of the project. You can find this on the [Sinch Dashboard](https://dashboard.sinch.com/convapi/apps).

## Request body:

  - `application/json` (unknown)
    This is the request body for sending a message. `app_id`, `recipient`, and `message` are all required fields.

## Request fields (application/json):

  - `app_id` (string, required)
    The ID of the app sending the message.
    Example: {APP_ID}

  - `callback_url` (string)
    Overwrites the default callback url for delivery receipts for this message.
Note that you may [define a `secret_for_overridden_callback_urls` at the app level](https://developers.sinch.com/docs/conversation/api-reference/conversation/tag/App/#tag/App/operation/App_UpdateApp!path=callback_settings/secret_for_overridden_callback_urls&t=request); this secret will be used to sign the contents of delivery receipts when the default callback URL is overridden by this property. The REST URL should be of the form: `http://host[:port]/path`

  - `channel_priority_order` (array)
    Explicitly define the channels and order in which they are tried when sending the message. All channels provided in this field must be configured in the corresponding Conversation API app, or the request will be rejected.
Which channels the API will try and their priority is defined by:
1. `channel_priority_order` if available.
2. `recipient.identified_by.channel_identities` if available.
3. When recipient is a `contact_id`:
  - if a conversation with the contact exists: the active channel of the conversation is tried first.
  - the existing channels for the contact are ordered by contact channel preferences if given.
  - lastly the existing channels for the contact are ordered by the app priority.

  - `channel_properties` (object)
    Channel-specific properties.
The key in the map must point to a valid channel property key as
defined by the enum ChannelPropertyKeys.
The maximum allowed property value length is 1024 characters.

  - `message` (object, required)
    A message originating from a Conversation API app

  - `message.explicit_channel_message` (object)
    Allows you to specify a channel and define a corresponding channel specific message payload that will override the standard Conversation API message types. The key in the map must point to a valid conversation channel as defined in the enum `ConversationChannel`. The message content must be provided in a string format. You may use the [transcoding endpoint](https://developers.sinch.com/docs/conversation/api-reference/conversation/tag/Transcoding/) to help create your message. For more information about how to construct an explicit channel message for a particular channel, see that [channel's corresponding documentation](https://developers.sinch.com/docs/conversation/channel-support/) (for example, using explicit channel messages with [the WhatsApp channel](https://developers.sinch.com/docs/conversation/channel-support/whatsapp/message-support/#explicit-channel-messages)).

  - `message.explicit_channel_omni_message` (object)
    Override the message's content for specified channels. The key in the map must point to a valid conversation channel as defined in the enum `ConversationChannel`. The content defined under the specified channel will be sent on that channel.

  - `message.channel_specific_message` (object)
    Channel specific messages, overriding any transcoding. The structure of this property is more well-defined than the open structure of the `explicit_channel_message` property, and may be easier to use.
The key in the map must point to a valid conversation channel as defined in the enum `ConversationChannel`.

  - `message.agent` (object)
    Represents an agent that is involved in a conversation.

  - `message.agent.display_name` (string)
    Agent's display name

  - `message.agent.type` (string)
    Agent's classification. It can be UNKNOWN_AGENT_TYPE, HUMAN or BOT.
    Enum: "UNKNOWN_AGENT_TYPE", "HUMAN", "BOT"

  - `message.agent.picture_url` (string)
    The Agent's picture url.

  - `message.reply_to` (object)
    Sends this message as a contextual reply to an inbound contact message, so the contact sees their original message quoted. Only supported on the WhatsApp channel. Conversation API keeps the mapping needed for the quote for 96 hours. If the referenced message is unknown or older than 96 hours, or the message is sent on a channel that does not support contextual replies, the message is still sent without the quote. For more information, see [Sending contextual replies](https://developers.sinch.com/docs/conversation/channel-support/whatsapp/message-support/#sending-contextual-replies).

  - `message.reply_to.message_id` (string, required)
    Required when using `reply_to`. The Conversation API ID of the inbound contact message this message replies to. Do not use a channel message ID (e.g., a WhatsApp message ID) from Meta.

  - `message.card_message` (object)
    Message containing text, media and choices.

  - `message.card_message.choices` (array)
    You may include choices in your Card Message. The number of choices is limited to 10.

  - `message.card_message.choices.postback_data` (any)
    An optional field. This data will be returned in the ChoiceResponseMessage. The default is message_id_{text, title}.

  - `message.card_message.choices.display_mode` (string)
    Controls the display behavior of a choice. Only supported for Choice Message on the RCS channel. Has no effect on other channels or message types, except for a carousel's outer choices, where it is rejected outright.
    Enum: "DISPLAY_MODE_UNSPECIFIED", "PERSISTENT"

  - `message.card_message.choices.call_message` (object)

  - `message.card_message.choices.call_message.phone_number` (string, required)
    Phone number in E.164 with leading +.
    Example: +15551231234

  - `message.card_message.choices.call_message.title` (string, required)
    Title shown close to the phone number.
The title is clickable in some cases.
    Example: Message text

  - `message.card_message.choices.location_message` (object)

  - `message.card_message.choices.location_message.coordinates` (object, required)

  - `message.card_message.choices.location_message.coordinates.latitude` (number, required)
    The latitude.

  - `message.card_message.choices.location_message.coordinates.longitude` (number, required)
    The longitude.

  - `message.card_message.choices.location_message.label` (string)
    Label or name for the position.

  - `message.card_message.choices.location_message.title` (string, required)
    The title is shown close to the button or link that leads to a map showing the location. The title can be clickable in some cases.

  - `message.card_message.choices.text_message` (object)

  - `message.card_message.choices.text_message.text` (string, required)
    The text to be sent.

  - `message.card_message.choices.url_message` (object)

  - `message.card_message.choices.url_message.title` (string, required)
    The title shown close to the URL. The title can be clickable in some cases.

  - `message.card_message.choices.url_message.url` (string, required)
    The url to show.

  - `message.card_message.choices.calendar_message` (object)

  - `message.card_message.choices.calendar_message.title` (string, required)
    The title is shown close to the button that leads to open a user calendar.

  - `message.card_message.choices.calendar_message.event_start` (string, required)
    The timestamp defines start of a calendar event.
    Example: 2025-11-30T10:00:00Z

  - `message.card_message.choices.calendar_message.event_end` (string, required)
    The timestamp defines end of a calendar event.
    Example: 2025-11-30T11:00:00Z

  - `message.card_message.choices.calendar_message.event_title` (string, required)
    Title of a calendar event.

  - `message.card_message.choices.calendar_message.event_description` (string)
    Description of a calendar event.

  - `message.card_message.choices.calendar_message.fallback_url` (string, required)
    The URL that is opened when the user cannot open a calendar event directly or channel does not have support for this type.

  - `message.card_message.choices.share_location_message` (object)

  - `message.card_message.choices.share_location_message.title` (string, required)
    The title is shown close to the button that leads to open a map to share a location.

  - `message.card_message.choices.share_location_message.fallback_url` (string, required)
    The URL that is opened when channel does not have support for this type.

  - `message.card_message.description` (string)
    This is an optional description field that is displayed below the title on the card.

  - `message.card_message.height` (string)
    You can set the desired size of the card in the message.
    Enum: "UNSPECIFIED_HEIGHT", "SHORT", "MEDIUM", "TALL"

  - `message.card_message.title` (string)
    The title of the card message.

  - `message.card_message.media_message` (object)
    A message containing a media component.

  - `message.card_message.media_message.thumbnail_url` (string)
    An optional parameter. Will be used where it is natively supported.

  - `message.card_message.media_message.url` (string, required)
    Url to the media file.

  - `message.card_message.media_message.filename_override` (string)
    Overrides the media file name.

  - `message.card_message.message_properties` (object)
    Optional additional properties.

  - `message.card_message.message_properties.whatsapp_header` (string)
    Optional. Sets the header for the footer of a WhatsApp reply button message, if there is no media in the message. Ignored for other channels. Ignored if not transcoded to a native WhatsApp message with reply buttons.

  - `message.carousel_message` (object)

  - `message.carousel_message.cards` (array, required)
    A list of up to 10 cards.

  - `message.carousel_message.choices` (array)
    Optional. Outer choices on the carousel level. The number of outer choices is limited to 3.

  - `message.choice_message` (object)
    Additional properties for the message.

  - `message.choice_message.choices` (array)
    The number of choices is limited to 10.

  - `message.choice_message.text_message` (object)

  - `message.choice_message.text_message.text` (string, required)
    The text to be sent.

  - `message.choice_message.message_properties` (object)

  - `message.choice_message.message_properties.whatsapp_footer` (string)
    Optional. Sets the text for the footer of a WhatsApp reply button or URL button message. Ignored for other channels.

  - `message.template_message` (object)

  - `message.template_message.channel_template` (object)
    Optional. Channel specific template reference with parameters per channel.
The channel template if exists overrides the omnichannel template.
At least one of `channel_template` or `omni_template` needs to be present.
The key in the map must point to a valid conversation channel as
defined by the enum ConversationChannel.

  - `message.template_message.omni_template` (object)
    The referenced template can be an omnichannel template stored in Conversation API Template Store as an AppMessage. You may also reference external channel-specific templates, such as a WhatsApp Business Template. Note that channel-specific template references are not supported when populating the `explicit_channel_omni_message` field.

  - `message.template_message.omni_template.version` (string, required)
    Used to specify what version of a template to use. Required when using `omni_channel_override` and `omni_template` fields.
This will be used in conjunction with `language_code`. Note that, when referencing omni-channel templates using the [Sinch Customer Dashboard](https://dashboard.sinch.com/), the latest version of a given omni-template can be identified by populating this field with `latest`.

  - `message.template_message.omni_template.language_code` (string)
    The BCP-47 language code, such as `en_US` or `sr_Latn`.
For more information, see http://www.unicode.org/reports/tr35/#Unicode_locale_identifier. English is the default `language_code`.
Note that, while many API calls involving templates accept either the dashed format (`en-US`) or the underscored format (`en_US`), some channel specific templates (for example, WhatsApp channel-specific templates) only accept the underscored format. Note that this field is required for WhatsApp channel-specific templates.

  - `message.template_message.omni_template.parameters` (object)
    Required if the template has parameters. Concrete values must
be present for all defined parameters
in the template. Parameters can be different for
different versions and/or languages of the template.

  - `message.template_message.omni_template.template_id` (string, required)
    The ID of the template. Note that, in the case of WhatsApp channel-specific templates, this field must be populated by the name of the template.

  - `message.list_message` (object)

  - `message.list_message.title` (string, required)
    A title for the message that is displayed near the products or choices.

  - `message.list_message.description` (string)
    This is an optional field, containing a description for the message.

  - `message.list_message.sections` (array, required)
    List of ListSection objects containing choices to be presented in the list message.

  - `message.list_message.sections.title` (string)
    Optional parameter. Title for list section.

  - `message.list_message.sections.items` (array, required)

  - `message.list_message.sections.items.choice` (object, required)
    A message component for interactive messages, containing a choice.

  - `message.list_message.sections.items.choice.title` (string, required)
    Required parameter. Title for the choice item.

  - `message.list_message.sections.items.choice.description` (string)
    Optional parameter. The description (or subtitle) of this choice item.

  - `message.list_message.sections.items.choice.media` (object)
    Optional parameter. The media of this choice item.

  - `message.list_message.sections.items.choice.postback_data` (string)
    Optional parameter. Postback data that will be returned in the MO if the user selects this option.

  - `message.list_message.sections.items.product` (object, required)
    A message component for interactive messages, containing a product.

  - `message.list_message.sections.items.product.id` (string, required)
    Required parameter. The ID for the product.

  - `message.list_message.sections.items.product.marketplace` (string, required)
    Required parameter. The marketplace to which the product belongs.
    Example: FACEBOOK

  - `message.list_message.sections.items.product.quantity` (integer)
    Output only. The quantity of the chosen product.

  - `message.list_message.sections.items.product.item_price` (number)
    Output only. The price for one unit of the chosen product.

  - `message.list_message.sections.items.product.currency` (string)
    Output only. The currency of the item_price.

  - `message.list_message.message_properties` (object)
    Additional properties for the message. Required if sending a product list message.

  - `message.list_message.message_properties.catalog_id` (string)
    Required if sending a product list message. The ID of the catalog to which the products belong.

  - `message.list_message.message_properties.menu` (string)
    Optional. Sets the text for the menu of a choice list message.

  - `message.list_message.message_properties.whatsapp_header` (string)
    Optional. Sets the text for the header of a WhatsApp choice list message. Ignored for other channels.

  - `message.contact_info_message` (object)

  - `message.contact_info_message.name` (object, required)
    Name information of the contact.

  - `message.contact_info_message.name.full_name` (string, required)
    Full name of the contact

  - `message.contact_info_message.name.first_name` (string)
    First name.

  - `message.contact_info_message.name.last_name` (string)
    Last name.

  - `message.contact_info_message.name.middle_name` (string)
    Middle name.

  - `message.contact_info_message.name.prefix` (string)
    Prefix before the name. e.g. Mr, Mrs, Dr etc.

  - `message.contact_info_message.name.suffix` (string)
    Suffix after the name.

  - `message.contact_info_message.phone_numbers` (array, required)
    Phone numbers of the contact

  - `message.contact_info_message.phone_numbers.phone_number` (string, required)
    Phone number with country code included.

  - `message.contact_info_message.phone_numbers.type` (string)
    Phone number type, e.g. WORK or HOME.

  - `message.contact_info_message.addresses` (array)
    Physical addresses of the contact

  - `message.contact_info_message.addresses.city` (string)
    City Name

  - `message.contact_info_message.addresses.country` (string)
    Country Name

  - `message.contact_info_message.addresses.state` (string)
    Name of a state or region of a country.

  - `message.contact_info_message.addresses.zip` (string)
    Zip/postal code

  - `message.contact_info_message.addresses.type` (string)
    Address type, e.g. WORK or HOME

  - `message.contact_info_message.addresses.country_code` (string)
    Two letter country code.

  - `message.contact_info_message.email_addresses` (array)
    Email addresses of the contact

  - `message.contact_info_message.email_addresses.email_address` (string, required)
    Email address.

  - `message.contact_info_message.email_addresses.type` (string)
    Email address type. e.g. WORK or HOME.

  - `message.contact_info_message.organization` (object)
    Organization information of the contact.

  - `message.contact_info_message.organization.company` (string)
    Company name

  - `message.contact_info_message.organization.department` (string)
    Department at the company

  - `message.contact_info_message.organization.title` (string)
    Corporate title, e.g. Software engineer

  - `message.contact_info_message.urls` (array)
    URLs/websites associated with the contact

  - `message.contact_info_message.urls.url` (string, required)
    The URL to be referenced

  - `message.contact_info_message.urls.type` (string)
    Optional. URL type, e.g. Org or Social

  - `message.contact_info_message.birthday` (string)
    Date of birth in YYYY-MM-DD format.

  - `message_metadata` (string)
    Metadata that should be associated with the message.
Returned in the `metadata` field of a [Message Delivery Receipt](https://developers.sinch.com/docs/conversation/callbacks/#message-delivery-receipt). Up to 1024 characters long.

  - `conversation_metadata` (object)
    Metadata that will be associated with the conversation in `CONVERSATION` mode and with the specified recipient identities in `DISPATCH` mode.
This metadata will be propagated on MO callbacks associated
with the respective conversation or user identity. Up to 2048 characters long.
Note that the MO callback will always use the last metadata available.
Important notes:
- If you send a message with the `conversation_metadata` field populated, and then send another message without populating the `conversation_metadata` field, the original metadata will continue be propagated on the related MO callbacks.
- If you send a message with the `conversation_metadata` field populated, and then send another message with a different value for `conversation_metadata` in the same conversation, the latest metadata value overwrites the existing one. So, future MO callbacks will include the new metadata.
- The `conversation_metadata` only accepts json objects.
- If you send a message in `DISPATCH` mode while the [retention period](https://developers.sinch.com/docs/conversation/api-reference/conversation/tag/App/#tag/App/operation/App_CreateApp!path=dispatch_retention_policy/ttl_days&t=request) of the app is set to 0 (note that this value is set to 0 by default), the `conversation_metadata` field will not be retained.

Currently only returned in the `message_metadata` field of an [Inbound Message](https://developers.sinch.com/docs/conversation/callbacks/#inbound-message) callback.

  - `queue` (string)
    Select the priority type for the message
    Enum: "NORMAL_PRIORITY", "HIGH_PRIORITY"

  - `recipient` (object, required)
    Identifies the recipient. If [Dispatch Mode](https://developers.sinch.com/docs/conversation/processing-modes/) is used, you must use the `identified_by` field.

  - `recipient.identified_by` (object)
    The identity as specified by the channel.

  - `recipient.identified_by.channel_identities` (array, required)
    A list of specific channel identities.
The API will use these identities when sending to specific channels.

  - `recipient.identified_by.channel_identities.identity` (string, required)
    The channel recipient identity.

  - `recipient.contact_id` (string)
    The ID of the contact.
    Example: {CONTACT_ID}

  - `ttl` (string)
    The timeout allotted for sending the message, expressed in seconds.
Passed to channels which support it and
emulated by the Conversation API for channels without ttl support
but with message retract/unsend functionality.
Channel failover will not be performed for messages with an expired TTL.
The format is an integer with the suffix `s` (for seconds).
Valid integer range is 3 to 315,576,000,000 (inclusive).
Example values include `10s` (10 seconds) and `86400s` (24 hours).

  - `processing_strategy` (string)
    Overrides the app's [Processing Mode](https://developers.sinch.com/docs/conversation/processing-modes/). Default value is `DEFAULT`.
    Enum: "DEFAULT", "DISPATCH_ONLY"

  - `correlation_id` (string)
    An arbitrary identifier that will be propagated to callbacks related to this message,
including MO messages from the recipient. The `correlation_id` is associated with the conversation in `CONVERSATION` mode and with the specified recipient identities in `DISPATCH` mode. The MO callbacks will always include the last `correlation_id` available,
(which is similar to how the `conversation_metadata` property functions).
Up to 128 characters long.
Important note: If you send a message in `DISPATCH` mode while the [retention period](https://developers.sinch.com/docs/conversation/api-reference/conversation/tag/App/#tag/App/operation/App_CreateApp!path=dispatch_retention_policy/ttl_days&t=request) of the app is set to 0 (note that this value is set to 0 by default), the `correlation_id` field will not be retained.

  - `conversation_metadata_update_strategy` (string)
    Update strategy for the `conversation_metadata` field. Only supported in `CONVERSATION` processing mode.
    Enum: "REPLACE", "MERGE_PATCH"

  - `message_content_type` (string)
    This field classifies the message content for use with Sinch's [consent management functionality](https://developers.sinch.com/docs/conversation/consent-management/). Note that this field is currently only used with Sinch's consent management functionality, and is not referenced elsewhere by the Conversation API.
    Enum: "CONTENT_UNKNOWN", "CONTENT_MARKETING", "CONTENT_NOTIFICATION"

## Request examples:

  - `Send message with identified_by recipient` (unknown)

  - `Card message` (unknown)
    An example payload of a card message.

  - `Carousel message` (unknown)
    An example payload of a carousel message.

  - `Choice message` (unknown)
    An example payload of a choice message.

  - `List message with choices` (unknown)
    An example message of a list message with choices

  - `List message with products` (unknown)
    An example message of a list message with products

  - `Location message` (unknown)
    An example payload of a location message.

  - `Media message` (unknown)
    An example message of a media message.

  - `Send message with contact_id recipient` (unknown)

  - `Send message using an omnichannel template` (unknown)

  - `Send explicit channel message, overriding omni message` (unknown)

## Response 200:

  - `200` (unknown)
    A successful response. More information is available in [delivery report callbacks](https://developers.sinch.com/docs/conversation/callbacks/).

## Response 200 fields (application/json):

  - `accepted_time` (string)
    Timestamp when the Conversation API accepted the message for delivery to the referenced contact.

  - `message_id` (string)
    The ID of the message.

## Response 400:

  - `400` (unknown)
    Malformed request. See [common error responses](https://developers.sinch.com/docs/conversation/api-reference/#common-error-responses) for more information.

## Response 400 fields (application/json):

  - `error` (object)

  - `error.code` (integer)

  - `error.details` (array)

  - `error.details.type_url` (string)

  - `error.details.value` (string)

  - `error.message` (string)

  - `error.status` (string)

## Response 401:

  - `401` (unknown)
    Incorrect credentials. See [common error responses](https://developers.sinch.com/docs/conversation/api-reference/#common-error-responses) for more information.

## Response 403:

  - `403` (unknown)
    Correct credentials but you don't have access to the requested resource. See [common error responses](https://developers.sinch.com/docs/conversation/api-reference/#common-error-responses) for more information.

## Response 403 fields (application/json):

  - `error` (object)

  - `error.code` (integer)

  - `error.details` (array)

  - `error.details.type_url` (string)

  - `error.details.value` (string)

  - `error.message` (string)

  - `error.status` (string)

## Response 500:

  - `500` (unknown)
    Correct credentials but you don't have access to the requested resource. See [common error responses](https://developers.sinch.com/docs/conversation/api-reference/#common-error-responses) for more information.

## Response 500 fields (application/json):

  - `error` (object)

  - `error.code` (integer)

  - `error.details` (array)

  - `error.details.type_url` (string)

  - `error.details.value` (string)

  - `error.message` (string)

  - `error.status` (string)

## Response 501:

  - `501` (unknown)
    Something went wrong on our end, try again with exponential back-off. See [common error responses](https://developers.sinch.com/docs/conversation/api-reference/#common-error-responses) for more information.

## Response 501 fields (application/json):

  - `error` (object)

  - `error.code` (integer)

  - `error.details` (array)

  - `error.details.type_url` (string)

  - `error.details.value` (string)

  - `error.message` (string)

  - `error.status` (string)