> For clean Markdown of any page, append .md to the page URL. > For a complete documentation index, see https://docs.astropods.com/llms.txt. > For AI client integration (Claude Code, Cursor, etc.), connect to the MCP server at https://docs.astropods.com/_mcp/server. # Inbound message anatomy An incoming message is a `Message`. The same shape applies whether it came from Slack, the web chat, or any other adapter. #### Node **`Message`** | Field | Type | Required | Notes | | ----------------- | ----------------- | -------- | ---------------------------------------------------------------------------------- | | `id` | string | yes | UUID assigned by the sidecar. | | `timestamp` | `Timestamp` | yes | When the platform received the message. | | `platform` | string | yes | `"slack"`, `"web"`, `"discord"`, etc. | | `platformContext` | `PlatformContext` | yes | Platform-native IDs and event metadata. | | `user` | `User` | yes | Sender identity. | | `content` | string | yes | Cleaned text. Adapters strip the bot's @-mention before forwarding. | | `attachments` | `Attachment[]` | no | Files, images, video, audio, link previews. | | `conversationId` | string | yes | Stable correlation ID across the message lifecycle. Always echo back on responses. | **`Timestamp`** (google.protobuf.Timestamp) | Field | Type | Notes | | --------- | ------ | ----------------------------------------------------------------------- | | `seconds` | string | Seconds since UNIX epoch. Encoded as a string (can exceed JS safe int). | | `nanos` | number | Nanoseconds within the second. | **`User`** | Field | Type | Required | Notes | | ----------- | --------------------------- | -------- | ------------------------------------------------- | | `id` | string | yes | Platform-specific user ID. | | `username` | string | no | Display name or handle. | | `avatarUrl` | string | no | Avatar URL. | | `email` | string | no | Email if available. | | `userData` | `{ [key: string]: string }` | no | Platform-specific extras (workspace, role, etc.). | **`Attachment`** | Field | Type | Required | Notes | | ------------- | ------ | -------- | -------------------------------------------------------------------------------------------------------------------------------- | | `type` | string | yes | One of the enum values below. | | `url` | string | no | Download URL when the source provides one. Filesystem-backed web uploads leave this empty. | | `filename` | string | no | Original filename. | | `sizeBytes` | number | no | File size in bytes. | | `mimeType` | string | no | MIME type. | | `title` | string | no | Display title (rich attachments). | | `description` | string | no | Display description. | | `width` | number | no | For images/videos. | | `height` | number | no | For images/videos. | | `storageKey` | string | no | Opaque Files API key for a web-chat upload. Resolve it through `AGENT_FILES_DIR`; never construct an input path from `filename`. | `Attachment.type` values: `TYPE_UNSPECIFIED`, `IMAGE`, `FILE`, `VIDEO`, `AUDIO`, `LINK`. **`PlatformContext`** | Field | Type | Required | Notes | | -------------- | --------------------------- | -------- | ---------------------------------------------------------------------------------------------- | | `messageId` | string | yes | Original platform message ID. | | `channelId` | string | yes | Channel/room/chat ID. | | `threadId` | string | no | Agent's reply target. Also set on top-level messages whose response should open a new thread. | | `threadRootId` | string | no | Parent thread root timestamp. Set only when this message is a reply inside an existing thread. | | `channelName` | string | no | Display channel name. | | `workspaceId` | string | no | Slack workspace, Discord guild, etc. | | `botUserId` | string | no | The bot's own user ID in the source platform. | | `userId` | string | no | Raw platform-native sender ID before any cross-platform identity resolution. | | `eventKind` | string | yes | See `PlatformContextEventKind` below. | | `platformData` | `{ [key: string]: string }` | no | Platform-specific extras (Slack `ts`, Discord snowflake, Teams activity ID). | **`PlatformContextEventKind`** | Value | When the adapter emits it | | ------------------------------------- | -------------------------------------------------- | | `EVENT_KIND_UNSPECIFIED` | Fallback. Should not appear in production traffic. | | `EVENT_KIND_DM` | 1:1 / private chat (Slack DM, web chat session). | | `EVENT_KIND_APP_MENTION` | Bot was @-mentioned in a channel or thread. | | `EVENT_KIND_THREAD_REPLY` | Reply inside an existing thread, no @-mention. | | `EVENT_KIND_OBSERVED` | Observe-channel forward (listen-only). | | `EVENT_KIND_REACTION` | Reaction added/removed. | | `EVENT_KIND_BUTTON_CLICK` | Interactive button click on a `CardAttachment`. | | `EVENT_KIND_SLASH_COMMAND` | Slash command (Slack/Discord). | | `EVENT_KIND_ASSISTANT_THREAD_STARTED` | Slack assistant thread opened. | #### Python **`Message`** | Field | Type | Required | Notes | | ------------------ | --------------------------- | -------- | ---------------------------------------------------------------------------------- | | `id` | string | yes | UUID assigned by the sidecar. | | `timestamp` | `google.protobuf.Timestamp` | yes | When the platform received the message. | | `platform` | string | yes | `"slack"`, `"web"`, `"discord"`, etc. | | `platform_context` | `PlatformContext` | yes | Platform-native IDs and event metadata. | | `user` | `User` | yes | Sender identity. | | `content` | string | yes | Cleaned text. Adapters strip the bot's @-mention before forwarding. | | `attachments` | `repeated Attachment` | no | Files, images, video, audio, link previews. | | `conversation_id` | string | yes | Stable correlation ID across the message lifecycle. Always echo back on responses. | **`User`** | Field | Type | Required | Notes | | ------------ | --------------------- | -------- | ------------------------------------------------- | | `id` | string | yes | Platform-specific user ID. | | `username` | string | no | Display name or handle. | | `avatar_url` | string | no | Avatar URL. | | `email` | string | no | Email if available. | | `user_data` | `map` | no | Platform-specific extras (workspace, role, etc.). | **`Attachment`** | Field | Type | Required | Notes | | ------------- | ------ | -------- | -------------------------------------------------------------------------------------------------------------------------------- | | `type` | enum | yes | See `Attachment.Type` below. | | `url` | string | no | Download URL when the source provides one. Filesystem-backed web uploads leave this empty. | | `filename` | string | no | Original filename. | | `size_bytes` | int64 | no | File size in bytes. | | `mime_type` | string | no | MIME type. | | `title` | string | no | Display title (rich attachments). | | `description` | string | no | Display description. | | `width` | int32 | no | For images/videos. | | `height` | int32 | no | For images/videos. | | `storage_key` | string | no | Opaque Files API key for a web-chat upload. Resolve it through `AGENT_FILES_DIR`; never construct an input path from `filename`. | **`Attachment.Type`**: `TYPE_UNSPECIFIED` (0), `IMAGE` (1), `FILE` (2), `VIDEO` (3), `AUDIO` (4), `LINK` (5). Access via `Attachment.IMAGE` etc. **`PlatformContext`** | Field | Type | Required | Notes | | ---------------- | --------------------- | -------- | ---------------------------------------------------------------------------------------------- | | `message_id` | string | yes | Original platform message ID. | | `channel_id` | string | yes | Channel/room/chat ID. | | `thread_id` | string | no | Agent's reply target. Also set on top-level messages whose response should open a new thread. | | `thread_root_id` | string | no | Parent thread root timestamp. Set only when this message is a reply inside an existing thread. | | `channel_name` | string | no | Display channel name. | | `workspace_id` | string | no | Slack workspace, Discord guild, etc. | | `bot_user_id` | string | no | The bot's own user ID in the source platform. | | `user_id` | string | no | Raw platform-native sender ID before any cross-platform identity resolution. | | `event_kind` | enum | yes | See `PlatformContext.EventKind` below. | | `platform_data` | `map` | no | Platform-specific extras (Slack `ts`, Discord snowflake, Teams activity ID). | **`PlatformContext.EventKind`** (access via `PlatformContext.EVENT_KIND_DM` etc.) | Value | When the adapter emits it | | ----------------------------------------- | -------------------------------------------------- | | `EVENT_KIND_UNSPECIFIED` (0) | Fallback. Should not appear in production traffic. | | `EVENT_KIND_DM` (1) | 1:1 / private chat (Slack DM, web chat session). | | `EVENT_KIND_APP_MENTION` (2) | Bot was @-mentioned in a channel or thread. | | `EVENT_KIND_THREAD_REPLY` (3) | Reply inside an existing thread, no @-mention. | | `EVENT_KIND_OBSERVED` (4) | Observe-channel forward (listen-only). | | `EVENT_KIND_REACTION` (5) | Reaction added/removed. | | `EVENT_KIND_BUTTON_CLICK` (6) | Interactive button click on a `CardAttachment`. | | `EVENT_KIND_SLASH_COMMAND` (7) | Slash command (Slack/Discord). | | `EVENT_KIND_ASSISTANT_THREAD_STARTED` (8) | Slack assistant thread opened. | For web-chat file input and agent-produced downloads, see [Files in chat](/messaging-sdk/files-in-chat). ## Next steps * [Sending a response](/messaging-sdk/responses): reply to what arrived * [Receiving platform feedback](/messaging-sdk/feedback): reactions, edits, and stream control