First bot

This example demonstrates a complete Discord bot using FastAPI Interactions, including environment variable configuration, multiple commands, and deferred responses with followups.

Setup

Environment variables are loaded from a .env file. Store your Discord credentials there:

APP_ID=123456789
PUBLIC_KEY=your_public_key_here
BOT_TOKEN=Bot your_bot_token_here

The bot

# main.py
from fastapi_interactions import Bot
from fastapi_interactions.commands import CommandRouter, Option
from fastapi_interactions.responses import DeferResponse
from environs import env
import asyncio

env.read_env()

APP_ID = env.int("APP_ID")
PUBLIC_KEY = env.str("PUBLIC_KEY")
BOT_TOKEN = env.str("BOT_TOKEN")

bot = Bot(app_id=APP_ID, public_key=PUBLIC_KEY, bot_token=BOT_TOKEN)

router = CommandRouter("router_a")

@router.command("username", "Returns your username")
async def username(ctx):
    return f"Your username is {ctx.user.username!r}"


@router.command("echo", "Repeat after me")
@Option.string("text", "Text to repeat back", required=True)
async def echo(ctx, text: str):
    async def finish():
        await asyncio.sleep(2)
        await ctx.send(f'Edits the original interaction message - {text!r}') # follow up message (edits the original interaction msg)
        await asyncio.sleep(2)
        await ctx.send('Sends a new message as response') # Follow up message sent as a reply to the original interaction msg
    return DeferResponse(finish=finish)


bot.attach_router(router)

# bot.sync_commands() # Run this only once and then comment out if necessary or use a secondary python script just to call sync commands
app = bot.app

Run

Simply use the fastapi cli to run it.

fastapi dev main.py

Ngrok

Use ngrok for local development and testing. Simply run your bot using fastapi cli and then

ngrok http 8000

Information

Make sure your ngrok url is set as your Discord app's interactions webhook url in the discord dev portal.

What's happening

username command — The simplest case. Returns immediately with a plain string, which the framework wraps in a MessageResponse automatically. ctx.user gives you the invoking user's data.

echo command — Demonstrates deferred responses. When invoked, Discord immediately receives a defer acknowledgement and shows "thinking..." to the user. Meanwhile, the finish async function runs in the background — it sleeps 2 seconds (simulating work), sends a followup message, sleeps again, then sends another followup. Each ctx.send() is a separate message, not edits.

Command syncing — bot.sync_commands() registers your commands with Discord. Run this once during deployment (it's skipped on preview builds), then comment it out. Global command registration can take up to an hour to propagate.