I built a small tool to test my own AI agent in 10 minutes, instead of trusting that it "looked right."

One test from it: "Find the JSON bug." The prompt is a single line:

const settings = JSON.parse('{"theme":"dark",}');

That trailing comma after "dark" is invalid JSON, so JSON.parse fails. The check is simple: name the trailing comma as the cause, show the smallest valid fix, and explain it.

I ran two answers through it:

  • A good answer — "The trailing comma after \"dark\" is invalid JSON. Fix: JSON.parse('{\"theme\":\"dark\"}')" — scored 4/4. What-to-fix: "No fix needed for this task."
  • A weak answer — "The JSON is broken because the theme value is wrong. Fix: change dark to light." — scored 3/4. It lost the "Is correct" point, because it never named the real cause. The plain-language fix: tell the agent the trailing comma is the problem, and to remove it without changing the value.

That is the whole point of the tool. It scores 4 things per task: finished, correct, did not make things up, and took no wrong action. Auto-score suggests, you confirm — so you get speed without handing the judgment to a black box.

The tool has 20 tasks: 10 developer, 5 personal-life, and 5 creator. It is free, with no API key, no login, and nothing leaves the page. It is a quick first check, not a CI or production replacement — use it first, then graduate to heavier tools when you need them.

Try this one task yourself: https://jefferson999.github.io/agent-reliability--score/

Paste your agent's answer, see the score, and read what to fix. If your agent spots the trailing comma, try the other 19.