> ## Documentation Index
> Fetch the complete documentation index at: https://docs.memorylake.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Append Conversation Message

> Append a message to a conversation

```
POST /openapi/memorylake/api/v3/conversations/{conversationId}/messages
```

Appends a new message to a conversation. Each message contains one or more content blocks (text, file, or both) and is attributed to an actor. MemoryLake automatically processes new messages to extract structured facts.

<Note>
  **Permission required:** `project:conv_append`
</Note>

### Path Parameters

<ParamField path="conversationId" type="string" required>
  Conversation identifier
</ParamField>

### Request Body

<ParamField body="content" type="array" required>
  Array of content blocks that make up the message body. Each block must include a `block_type` field.

  Accepted `block_type` values: `TEXT`, `FILE`, `IMAGE`, `THINKING`, `TOOL_USE`, `TOOL_RESULT`.

  **Text block:** `{ "block_type": "TEXT", "text": "message content" }`

  **Image block:** `{ "block_type": "IMAGE", "uri": "drive://...", "mime_type": "image/png" }`
</ParamField>

<ParamField body="actor_id" type="string" required>
  ID of the actor sending this message. Should reference an actor participating in the conversation.
</ParamField>

<ParamField body="timestamp" type="string">
  ISO 8601 timestamp for when the message originally occurred. Use this when ingesting historical conversations so MemoryLake preserves the original timeline.
</ParamField>

<ParamField body="metadata" type="object">
  Arbitrary key-value metadata to attach to the message
</ParamField>

<ParamField body="custom_id" type="string" required>
  Caller-defined unique identifier for the message within the conversation
</ParamField>

<ParamField body="parent_message_id" type="string">
  ID of the parent message, for threaded conversations. When set, this message is treated as a reply to the specified parent.
</ParamField>

<RequestExample>
  ```bash Text message theme={null}
  curl -X POST 'https://app.memorylake.ai/openapi/memorylake/api/v3/conversations/conv_7d2e3f4a5b6c7d8e/messages' \
    -H 'Authorization: Bearer sk_xxxxxx' \
    -H 'Content-Type: application/json' \
    -d '{
      "content": [
        {
          "block_type": "TEXT",
          "text": "Can you summarize last quarter'\''s revenue numbers?"
        }
      ],
      "actor_id": "actor_user_jane",
      "timestamp": "2025-06-01T14:10:00Z",
      "metadata": {
        "source": "web-app"
      }
    }'
  ```

  ```bash Image attachment theme={null}
  curl -X POST 'https://app.memorylake.ai/openapi/memorylake/api/v3/conversations/conv_7d2e3f4a5b6c7d8e/messages' \
    -H 'Authorization: Bearer sk_xxxxxx' \
    -H 'Content-Type: application/json' \
    -d '{
      "content": [
        {
          "block_type": "TEXT",
          "text": "Here is the chart for your review."
        },
        {
          "block_type": "IMAGE",
          "uri": "drive://items/item_abc123/chart.png",
          "mime_type": "image/png"
        }
      ],
      "actor_id": "actor_assistant_v2",
      "timestamp": "2025-06-01T14:10:30Z"
    }'
  ```

  ```bash Threaded reply theme={null}
  curl -X POST 'https://app.memorylake.ai/openapi/memorylake/api/v3/conversations/conv_7d2e3f4a5b6c7d8e/messages' \
    -H 'Authorization: Bearer sk_xxxxxx' \
    -H 'Content-Type: application/json' \
    -d '{
      "content": [
        {
          "block_type": "TEXT",
          "text": "Good point — I'\''ve updated the figures in the attached version."
        }
      ],
      "actor_id": "actor_user_jane",
      "parent_message_id": "msg_9e4b2c3d5f6a7b8c"
    }'
  ```
</RequestExample>

### Response

<ResponseField name="data" type="object">
  <Expandable title="Message object">
    <ResponseField name="id" type="string">Unique message identifier</ResponseField>

    <ResponseField name="content" type="array">
      Array of content blocks that make up the message body

      <Expandable title="Content block">
        <ResponseField name="block_type" type="string">Block type: `TEXT`, `FILE`, `IMAGE`, `THINKING`, `TOOL_USE`, `TOOL_RESULT`</ResponseField>
        <ResponseField name="text" type="string">Text content (present when `block_type` is `TEXT`)</ResponseField>
        <ResponseField name="uri" type="string">Drive resource URI (present when `block_type` is `IMAGE`)</ResponseField>
        <ResponseField name="mime_type" type="string">MIME type of the image (present when `block_type` is `IMAGE`)</ResponseField>
      </Expandable>
    </ResponseField>

    <ResponseField name="metadata" type="object">Arbitrary key-value metadata attached to the message</ResponseField>
    <ResponseField name="timestamp" type="string">Caller-provided timestamp for when the message originally occurred (ISO 8601)</ResponseField>
    <ResponseField name="conversation_id" type="string">ID of the conversation this message belongs to</ResponseField>
    <ResponseField name="sequence_no" type="integer">Position of this message within the conversation</ResponseField>
    <ResponseField name="actor_id" type="string">ID of the actor who sent this message</ResponseField>
    <ResponseField name="actor_type" type="string">Type of the actor: `HUMAN` or `ASSISTANT`</ResponseField>
    <ResponseField name="created_at" type="string">Creation timestamp</ResponseField>
  </Expandable>
</ResponseField>

<ResponseExample>
  ```json Success (200) theme={null}
  {
    "success": true,
    "data": {
      "id": "msg_3f4a5b6c7d8e9f0a",
      "content": [
        {
          "block_type": "TEXT",
          "text": "Can you summarize last quarter's revenue numbers?"
        }
      ],
      "metadata": {
        "source": "web-app"
      },
      "timestamp": "2025-06-01T14:10:00Z",
      "conversation_id": "conv_7d2e3f4a5b6c7d8e",
      "sequence_no": 3,
      "actor_id": "actor_user_jane",
      "created_at": "2025-06-01T14:10:05Z"
    }
  }
  ```
</ResponseExample>