Agents and tool use
Let an agent choose tools without letting it grant itself access.
Reviewed: 2026-10-03
Source-based teaching example · Fictional data
Narration: Microsoft Mark · locally synthesized

00:00:00.000 — What you will learn

Let an agent choose tools without letting it grant itself access.

Visual description:
Let an agent choose tools without letting it grant itself access.

00:00:06.875 — The idea

A model may propose an action. Application code must check the tool, inputs and permissions before running it. Keep limits on calls, time and repeated failures.

Visual description:
A model may propose an action. Application code must check the tool, inputs and permissions before running it. Keep limits on calls, time and repeated failures.

00:00:21.292 — One useful term

Agent. A system that uses model outputs to select actions and observe their results within an allowed task.

Visual description:
A system that uses model outputs to select actions and observe their results within an allowed task.

00:00:31.125 — A worked example

The mock model requests a document as a guest. The tool blocks access. The model then claims success, but no successful tool result supports that claim.

Visual description:
The mock model requests a document as a guest. The tool blocks access. The model then claims success, but no successful tool result supports that claim.

00:00:45.083 — Your turn to think

Can the answer cite a document after the read was denied? Pause and decide before continuing.

Visual description:
Can the answer cite a document after the read was denied?
Pause the video if you need more time.

00:01:02.042 — Why this answer works

No. Use actual tool results, not the model’s claim. A repeated-read loop must also stop at its allowed call limit.

Visual description:
No. Use actual tool results, not the model’s claim. A repeated-read loop must also stop at its allowed call limit.

00:01:13.417 — Check 1

Check permission before execution.

Visual description:
Check permission before execution.

00:01:18.542 — Check 2

Track actual tool outcomes.

Visual description:
Track actual tool outcomes.

00:01:23.583 — Check 3

Enforce stop limits outside the prompt.

Visual description:
Enforce stop limits outside the prompt.

00:01:29.125 — Now try a different case

Open the lesson and try its different practice case. Use every check in the full task. Watching alone does not mark the lesson complete.

Visual description:
Open the lesson
Try the new case
Check and revise
The full task and its requirements are in the linked lesson.