The File slot type enables plugins to receive file attachments from users. It is resolved only when the user interacts with the dedicated "Upload file" button in the assistant interface.

File Object Structure

The File slot accepts an object with the following structure:

{
  "file_name": string, // Name used when uploading to the customer API
  "location": string,  // File ID from input arguments
  "content": string   // Base64-encoded file contents
}

Supported file extensions (case-insensitive)

(case-insensitive)

.png, .jpg, .jpeg, .pdf, .txt, .csv, .xlsx, .xlsm, .xls, .xltx, .xltm

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Callout: Only these extensions are allowed as ticket attachments. Attempts to upload unsupported types will fail validation.

Upload Interface

Users must use the "Upload file" button.

Limitations

Limitation	Details
No file delivery to users	Files cannot be sent back to end users in chat responses.
No content manipulation	The system cannot read, parse, or modify file contents beyond base64 encoding.
Upload only via dedicated button	Uploading files directly in chat (e.g., Slack drag-and-drop) will not populate the `File` slot — it triggers BriefMe instead. Use only the "Upload file" pop-up that appears when the `File` slot is requested.
Multiple files not supported	`List[File]` is not supported. Even if the platform (e.g., Slack) allows selecting multiple files in the upload dialog, only the first file is processed. Subsequent files are ignored.

Workarounds

Use Case: Avoid Local File Download

Problem:

You do not want users to download files to their machine. Instead, you want users to paste a link (e.g., from Google Drive, OneDrive, or internal file server) directly into the assistant.

Limitation:

The platform cannot download files from external URLs on behalf of the user.

Solution:

Use a string slot named file_link instead of File.

Customer API responsibility:

Your API will need to handle the file download from the link passed by the user.

Download file from file_url
Validate content/type
Process as needed

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This bypasses local upload entirely. No file is stored or transmitted through the assistant.