Files

Files uploaded through the public API are draft file resources scoped to an Agent API Endpoint App. Mount them when creating a Thread or sending a user message. Files produced by the Agent are artifacts. Both appear in the Thread file list when visible to the API token caller.

Upload flow

Public uploads use multipart/form-data and accept files up to 67108864 bytes.

Upload the file to the Agent with POST /agents/{agentId}/files.
Store the returned file.id.
Mount the file with resources when creating a Thread or sending a later user message.

Upload a file

printf 'Customer asks for an implementation plan.' > brief.txt

curl -X POST "https://try.mosoo.ai/api/v1/agents/$MOSOO_AGENT_ID/files" \
  -H "Authorization: Bearer $MOSOO_API_TOKEN" \
  -F "file=@brief.txt;type=text/plain"

The response is a PublicFileResponse. Store file.id:

{
  "file": {
    "id": "01J0000000000000000000000J",
    "name": "brief.txt",
    "mimeType": "text/plain",
    "size": 41,
    "createdAt": "2026-05-19T00:02:00.000Z"
  }
}

Use a file in the first message

curl -X POST "https://try.mosoo.ai/api/v1/agents/$MOSOO_AGENT_ID/threads" \
  -H "Authorization: Bearer $MOSOO_API_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "resources": [
      {
        "type": "file",
        "file_id": "01J0000000000000000000000J"
      }
    ],
    "input": {
      "type": "user.message",
      "content": [
        {
          "type": "text",
          "text": "Summarize the attached file."
        }
      ]
    }
  }'

Use a file in a later message

Send the file ID in resources on a later user message:

{
  "events": [
    {
      "type": "user_message",
      "resources": [
        {
          "type": "file",
          "file_id": "01J0000000000000000000000J"
        }
      ],
      "text": "Summarize the attached file."
    }
  ]
}