Discord Webhook Relay MCP

An MCP server that does one thing: takes a Discord webhook URL and a message, and sends the message to Discord. Built with the MCP TypeScript SDK's Hono middleware, running on Cloudflare Workers.

Stack

• Runtime: Cloudflare Workers
• MCP: @modelcontextprotocol/server + @modelcontextprotocol/hono
• Framework: Hono
• Language: TypeScript
• Test: Vitest + @cloudflare/vitest-pool-workers
• Linter/Formatter: Biome

Getting Started

bun install
bun run dev

http://localhost:8787/ is the MCP endpoint (Streamable HTTP).

Tool

send_discord_message

Parameter	Type	Description
webhookUrl	string	The destination Discord webhook URL
message	string	The message to send (1–2000 characters)

webhookUrl is validated to match the shape of a Discord webhook URL, then the server sends POST { content: message } to it.

Commands

Command	Description
bun run dev	Start local dev server
bun run deploy	Deploy to Cloudflare Workers
bun run test	Run tests
bun run check	Lint and format check
bun run check:fix	Auto-fix lint and format issues
bun run cf-typegen	Generate Cloudflare binding types

Project Structure

src/
  index.ts   # MCP server and Hono app entry point
wrangler.jsonc # Wrangler configuration

Notes

• Cloudflare Workers has no concept of a local bind, so createMcpHonoApp's default localhost-only DNS-rebinding protection is disabled via host: "0.0.0.0" (see src/index.ts). Restrict it further with allowedHosts if you need to lock it down to your deployed hostname.
• The webhook URL is passed in as a tool argument on every call, so the server never stores or needs to hold a secret for it.