Support for File Upload in Plugin/Tool Actions — Markdown-to-PDF Conversion Use Case

[DevDema]

Hello LibreChat team,

I’m trying to set up an integration where LibreChat can send a Markdown file to an API endpoint (Stirling PDF) for conversion to PDF, and then return the PDF to the user. The endpoint (and my desired workflow) relies on a multipart/form-data POST request with a file upload (not just string content).

My use case:

• User: Uploads a Markdown file in LibreChat and requests a PDF conversion.
• LibreChat: Sends the Markdown file (using a plugin/tool/action) to POST /api/v1/convert/markdown/pdf (Stirling PDF API), with the Markdown file as a multipart form upload field called fileInput.
• Response: LibreChat receives the PDF from the endpoint and returns it to the user.

What I’ve tried:

• I created an OpenAPI 3.0 spec with the correct properties (type: string, format: binary) for the file field, matched to OpenAPI file upload guidelines.
• The endpoint works perfectly with curl, Swagger UI, and Postman (when using the file upload field and sending proper multipart form data).
• However, LibreChat’s plugin/tool interface only provides a text box for the file field instead of a file upload control, resulting in a 400 error from the API because it receives a string instead of a real file.
• The backend error from the API is:

  Failed to convert property value of type 'java.lang.String' to required type 'org.springframework.web.multipart.MultipartFile' for property 'fileInput'
  

• This makes me believe LibreChat does not yet support file uploads through plugins/tools, even when the OpenAPI spec defines the input as a format: binary string.

My question / request:

Does LibreChat currently support plugins/tools with file upload fields (multipart form), defined as type: string, format: binary in the OpenAPI spec?

• If this is not supported yet, are there workarounds, or is support planned?
• If it is supported, are there any additional configurations or syntax I need to enable file upload fields in the UI and correct POST requests in backend actions?
• Would you be able to point to an example of a working file-upload plugin/action/tool for reference?

Thanks for your help!
(If a feature request is appropriate, please let me know and I’ll file one.)

Action definition

openapi: 3.0.0
info:
  title: Markdown to PDF
  version: 1.0.0
servers:
  - url: http://stirling-pdf:8080
paths:
  /api/v1/convert/markdown/pdf:
    post:
      summary: Converts a Markdown file (uploaded as fileInput) to PDF
      requestBody:
        required: true
        content:
          multipart/form-data:
            schema:
              type: object
              properties:
                fileInput:
                  type: string
                  format: binary
                  description: The Markdown file to upload and convert
              required:
                - fileInput
      responses:
        '200':
          description: Returns the resulting PDF
          content:
            application/pdf:
              schema:
                type: string
                format: binary
                ```
**References:**
- [OpenAPI 3 — File Uploads](https://swagger.io/docs/specification/describing-request-body/file-upload/)
- [Stirling PDF API docs](https://github.com/Stirling-Tools/Stirling-PDF)