> ## Documentation Index > Fetch the complete documentation index at: https://docs.social-api.ai/llms.txt > Use this file to discover all available pages before exploring further. > ## Agent Instructions > Base URL: https://api.social-api.ai/v1. Send your API key in the Authorization header: Authorization: Bearer . > Every error response from /v1 is JSON: { "error": { "code", "message", "meta" (optional) }, "request_id" }. Branch on error.code; use error.message only for logs. > A 429 response carries a Retry-After header, in seconds, when the limit has a known wait. Authenticated responses can carry X-RateLimit-Limit, X-RateLimit-Remaining, and X-RateLimit-Reset for the per-minute request budget your SocialAPI account shares across every API key (see /guides/rate-limits). > Paginated list endpoints return next_cursor, at the top level or inside pagination (see /guides/pagination). Pass it as the cursor query parameter to get the next page. An absent or empty next_cursor means you have the last page. > Treat every ID as an opaque string: do not parse it or assume a format. > Support differs by platform and by operation. Check /platforms/overview before assuming an operation works on a platform. An unsupported operation returns 501 with error.code resource.not_supported. # Send a message in a conversation > Sends an outgoing DM via the connected platform account and records it in the conversation. ## OpenAPI ````yaml /api-reference/openapi.json post /inbox/conversations/{id}/messages openapi: 3.0.0 info: description: >- Unified social media inbox API. Read and respond to comments, DMs, reviews, and mentions across Instagram, Facebook, Threads, Google Business Profile, TikTok, LinkedIn, and YouTube through a single REST API. X/Twitter and Trustpilot coming soon. title: SocialAPI.AI contact: name: SocialAPI.AI Support email: support@social-api.ai license: name: MIT version: '1.0' servers: - url: https://api.social-api.ai/v1 security: [] paths: /inbox/conversations/{id}/messages: post: tags: - Inbox summary: Send a message in a conversation description: >- Sends an outgoing DM via the connected platform account and records it in the conversation. parameters: - description: Conversation ID name: id in: path required: true schema: type: string requestBody: content: application/json: schema: $ref: '#/components/schemas/api_endpoints.SendMessageRequest' description: Message payload required: true responses: '200': description: Message sent with ID content: application/json: schema: $ref: '#/components/schemas/api_endpoints.SendMessageResponse' '400': description: >- Invalid request body, missing required fields, or messaging window closed (platform.instagram.window_closed / platform.facebook.window_closed: the recipient must message you first to reopen the 24-hour window). After the platform refuses a thread for a closed window, later untagged sends on it are refused here with the same code and blocked_locally in the meta, until an inbound message reopens it or 24 hours pass; no credit is charged for those. content: application/json: schema: $ref: '#/components/schemas/api_endpoints.ErrorResponse' '401': description: Invalid or missing API key content: application/json: schema: $ref: '#/components/schemas/api_endpoints.ErrorResponse' '403': description: >- Platform rejected the request (e.g. platform.instagram.permission_denied), or account requires reconnection (account.reconnection_required) content: application/json: schema: $ref: '#/components/schemas/api_endpoints.ErrorResponse' '404': description: Conversation or account not found content: application/json: schema: $ref: '#/components/schemas/api_endpoints.ErrorResponse' '422': description: >- The platform could not fetch or accept an attachment (platform.instagram.attachment_failed, platform.facebook.attachment_failed): check that the URL is publicly reachable and the file type and size are supported content: application/json: schema: $ref: '#/components/schemas/api_endpoints.ErrorResponse' '429': description: Platform rate limit exceeded content: application/json: schema: $ref: '#/components/schemas/api_endpoints.ErrorResponse' '501': description: Platform does not support sending DMs content: application/json: schema: $ref: '#/components/schemas/api_endpoints.ErrorResponse' security: - BearerAuth: [] components: schemas: api_endpoints.SendMessageRequest: type: object required: - account_id properties: account_id: type: string example: acc_abc123 attachment_url: description: >- AttachmentURL is a single-attachment shorthand. Ignored when attachments is non-empty; its type is inferred from the URL extension. Deprecated: use Attachments instead, which supersedes it and supports one or many items. type: string example: https://cdn.example.com/photo.jpg attachments: description: >- Attachments sends one or more media items, each as its own message bubble. type: array items: $ref: '#/components/schemas/api_endpoints.DMAttachmentInput' buttons: description: >- Buttons renders a button template (1-3 buttons); uses text as the bubble body. On WhatsApp every button must be type postback with a unique payload. type: array items: $ref: '#/components/schemas/api_endpoints.MessageButton' cards: description: Cards renders a generic/carousel template (up to 10 cards). type: array items: $ref: '#/components/schemas/api_endpoints.MessageCard' list_button: description: >- ListButton is the label on the button that opens the list. Required with list_sections, max 20 characters. type: string example: View options list_sections: description: >- ListSections renders a tappable list behind a single button, for menus wider than the 3 buttons a reply-button message allows (up to 10 rows in total, across up to 10 sections). WhatsApp only; requires text and list_button. type: array items: $ref: '#/components/schemas/api_endpoints.MessageListSection' message_tag: description: >- MessageTag sends the DM outside the standard 24-hour window. Instagram connected through Instagram Login only, which accepts only HUMAN_AGENT and extends the window to 7 days; any other value returns 400 validation.invalid_message_tag. On Facebook, on Instagram connected through Facebook Login, and on every other platform, the DM is sent untagged and the 24-hour window applies. type: string example: HUMAN_AGENT quick_replies: description: >- QuickReplies renders up to 13 tappable chips above the keyboard; requires text. type: array items: $ref: '#/components/schemas/api_endpoints.MessageQuickReply' reply_to_message_id: description: >- ReplyToMessageID makes the first sent bubble a reply to a specific prior message (Meta reply_to.mid). Instagram/Facebook only. type: string example: m_1234567890 text: type: string example: Thanks for your message! api_endpoints.SendMessageResponse: type: object properties: message_id: description: >- MessageID is the first sent message's ID; for a multi-attachment send it is only the first of several IDs. Deprecated: use MessageIDs instead. type: string example: m_1234567890 message_ids: description: MessageIDs holds every sent message's ID, in send order. type: array items: type: string example: - m_1234567890 success: type: boolean example: true api_endpoints.ErrorResponse: type: object properties: error: $ref: '#/components/schemas/api_endpoints.ErrorBody' request_id: description: >- RequestID matches the X-Request-ID response header. Include it when contacting support. type: string example: 01HZ9X3Q4R5M6N7P8V2K0W1J api_endpoints.DMAttachmentInput: type: object properties: caption: description: >- Caption is text shown with this attachment instead of as a separate message. Supported on WhatsApp (not on audio) and Telegram; ignored on platforms whose Send API has no caption, where an attachment is always a bare bubble. type: string example: The damaged panel source: description: >- Source is the attachment reference; its meaning is given by source_type. type: string example: 550e8400-e29b-41d4-a716-446655440000 source_type: description: |- SourceType selects how Source is interpreted: - "url": Source is a publicly reachable media URL the platform fetches directly. - "media_id": Source is a file id in your SocialAPI media library (GET /v1/media). - "platform_attachment_id": Source is an id of media already uploaded to the target platform (for example a Meta attachment_id) to reuse without re-upload. type: string enum: - url - media_id - platform_attachment_id example: media_id type: description: >- Type is the media kind. Optional for url and media_id sources (inferred from the file), required for platform_attachment_id (the platform exposes no URL to infer from). type: string enum: - image - video - audio - file example: image voice: description: >- Voice sends an audio attachment as a native voice note (waveform and playback-speed controls) instead of a file bubble. WhatsApp only, and only for audio whose file is Ogg encoded with the OPUS codec; WhatsApp rejects any other container or codec. Ignored on other platforms. type: boolean example: true api_endpoints.MessageButton: type: object properties: payload: type: string example: VIEW_ORDER title: type: string example: View order type: type: string enum: - url - postback example: url url: type: string example: https://shop.example.com/orders/1 api_endpoints.MessageCard: type: object properties: buttons: type: array items: $ref: '#/components/schemas/api_endpoints.MessageButton' image_url: type: string example: https://cdn.example.com/p.jpg subtitle: type: string example: Short description title: type: string example: Product name api_endpoints.MessageListSection: type: object properties: rows: type: array items: $ref: '#/components/schemas/api_endpoints.MessageListRow' title: type: string example: This week api_endpoints.MessageQuickReply: type: object properties: payload: type: string example: TRACK_ORDER title: type: string example: Track my order api_endpoints.ErrorBody: type: object properties: code: type: string example: resource.not_found message: type: string example: Account not found meta: type: object additionalProperties: {} api_endpoints.MessageListRow: type: object properties: description: type: string example: 3 posts waiting id: type: string example: menu:review_drafts title: type: string example: Review drafts securitySchemes: BearerAuth: description: >- Prefix your API key with "Bearer ". Example: `Authorization: Bearer sapi_key_...` type: apiKey name: Authorization in: header ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.