Your AI API bill can double overnight and you won't know until the invoice. Here's a 20-line fix.

I run a swarm of AI agents that call LLM APIs all day. One night a retry loop went haywire and burned through 3 days of budget in two hours. I didn't find out until the invoice email the next morning.

That's the problem with API spend: there's no dashboard that pings you the moment something goes wrong. You have to go look for it.

So I wrote a small stdlib-only Python script that watches a CSV of your daily spend and fires a Slack or Discord webhook the moment you cross a threshold. No dependencies, no cloud service, no API keys beyond the webhook URL.

Most cost trackers already dump a CSV with a cost_usd column (OpenAI, Anthropic, your own logging — doesn't matter which). You just need something that reads today's total and screams if it's too high.

import csv import json import sys import urllib.request from datetime import date def today_spend ( csv_path, date_col = " date ", cost_col = " cost_usd " ): total = 0.0 today = date. today (). isoformat () with open ( csv_path, newline = "" ) as f: for row in csv. DictReader ( f ): if row [ date_col ] == today: total += float ( row [ cost_col ]) return total def send_webhook ( url, message ): payload = json. dumps ({ " content ": message }). encode () req = urllib. request. Request ( url, data = payload, headers = { " Content-Type ": " application/json " }) urllib. request. urlopen ( req, timeout = 10 ) def check ( csv_path, threshold, webhook_url, dry_run = False ): spend = today_spend ( csv_path ) if spend >= threshold: msg = f " ⚠️ Spend alert: $ { spend:.

2 f } today (threshold $ { threshold:. 2 f } ) " if dry_run: print ( " [DRY RUN] ", msg ) else: send_webhook ( webhook_url, msg ) return 2 # exit code your cron/scheduler can check for return 0 if __name__ == " __main__ ": code = check ( sys. argv [ 1 ], float ( sys. argv [ 2 ]), sys. argv [ 3 ], dry_run = " --dry-run " in sys. argv ) sys. exit ( code ) Enter fullscreen mode Exit fullscreen mode Run it from cron (or your agent scheduler) every 30 minutes:

python spend_alert.py usage.csv 10.00 https://discord.com/api/webhooks/XXXX --dry-run Enter fullscreen mode Exit fullscreen mode Drop --dry-run once you trust it. The nonzero exit code is the useful part — you can chain it into a kill-switch that pauses your agents the second spend crosses the line, instead of finding out from a billing email.

That's it. No dashboard login, no third-party SaaS reading your API keys, just a text file and a webhook.

I packaged the full version (plus a sample CSV and README) as a free/pay-what-you-want download here: https://renevibe76.gumroad.com/l/djlwjm

How do you currently find out your API spend jumped — do you check manually, or has something ever caught you by surprise before the invoice did?