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Add send_file / attachment support to built-in MCP send_message tool #35

@jrejaud

Description

@jrejaud

Feature Request

The built-in MCP server in Beeper Desktop (at localhost:23373/v0/mcp) exposes a send_message tool that only supports text. However, the REST API already supports file attachments via a two-step flow:

  1. Upload file via POST /v1/assets/upload (multipart) → returns uploadID
  2. Send message via POST /v1/chats/{chatID}/messages with attachment.uploadID

Request

Add either:

  • An attachment parameter to the existing send_message MCP tool (accepting a file path or base64 data)
  • A new send_file MCP tool that handles upload + send in one step

Why

File/image/video sharing is a core messaging feature. The REST API already supports it — the MCP tool just doesn't expose it. This means AI assistants using the MCP can't send files without dropping down to raw REST API calls.

Workaround

I built a stdio proxy that intercepts tools/list to inject a custom send_file tool, and handles the upload+send flow via the REST API. Published as beeper-mcp-file-proxy for anyone who needs this before native support lands.

Environment

  • Beeper Desktop v4.2.653
  • macOS
  • Using MCP with Claude Code

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