This snippet is an example of how to use the "message.create.prefix" event to create a simple prefix command, "!echo". Only messages starting with "!echo" will trigger this endpoint, so no "if" statement is needed. The event has the same fields as the "message.create" event.
const lib = require('lib')({token: process.env.STDLIB_SECRET_TOKEN});
await lib.discord.channels['@0.2.1'].messages.create({
channel_id: `${context.params.event.channel_id}`,
content: `Hey! You just said: ${context.params.event.content}`
});