When the Tool Says No
The most common agent failure, and the recovery that defines a good one.
When the Tool Says No is a free AI Agents lesson on CoddyKit — lesson 2 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the AI Agents learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.
Agents fail constantly. The interesting question is never "did it fail" — it is "what did it do next".
This run starts badly on purpose.
[{"type":"USER","text":"Is it raining where I am?"},
{"type":"THOUGHT","text":"I will check the weather."},
{"type":"TOOL_CALL","tool":"weather.get","args":{}},
{"type":"ERROR","tool":"weather.get","text":"missing required argument: 'city'"},
{"type":"THOUGHT","text":"I called it without a city. The profile says Ankara — retry with that."},
{"type":"TOOL_CALL","tool":"weather.get","args":{"city":"Ankara"}},
{"type":"TOOL_RESULT","tool":"weather.get","result":{"temp_c":16,"rain_chance":0.2,"simulated":true}},
{"type":"ANSWER","text":"Not right now — 20% chance in Ankara. (Reading is simulated.)"}]The recovery is the skill. An agent that repeats the identical failing call is not persistent, it is stuck — and every repeat costs another model call.
Your turn.
Frequently asked questions
Is the “When the Tool Says No” lesson free?
Yes — the full text of “When the Tool Says No” is free to read here on the web, and the AI Agents course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the AI Agents course, upgrade to CoddyKit PRO.
What will I learn in “When the Tool Says No”?
The most common agent failure, and the recovery that defines a good one. You practise AI Agents with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start AI Agents?
No prior experience is required. AI Agents on CoddyKit is structured for beginners through advanced learners; this is — lesson 2 of 4, so you can start here or from the beginning and move at your own pace.
How long does the “When the Tool Says No” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this AI Agents lesson?
Yes. Every AI Agents lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- The Loop
- When the Tool Says No
- Grounded or Guessing
- Budgets and Guardrails