Retrieval-augmented generation, from scratch
Give an AI answer relevant evidence and check whether it used it.
Reviewed: 2026-10-03
Source-based teaching example · Fictional data
Narration: Microsoft Mark · locally synthesized

00:00:00.000 — What you will learn

Give an AI answer relevant evidence and check whether it used it.

Visual description:
Give an AI answer relevant evidence and check whether it used it.

00:00:06.500 — The idea

First find the right source passage. Then check the answer against it. A failed search and an answer that contradicts retrieved evidence are different problems.

Visual description:
First find the right source passage. Then check the answer against it. A failed search and an answer that contradicts retrieved evidence are different problems.

00:00:19.208 — One useful term

RAG. Retrieval-augmented generation: finding source information and supplying it to a model when it answers.

Visual description:
Retrieval-augmented generation: finding source information and supplying it to a model when it answers.

00:00:29.500 — A worked example · 1

The workshop documents contain a time and room. A search may miss the relevant passage. Or it may find the time, while the answer states a different one.

Visual description:
The workshop documents contain a time and room. A search may miss the relevant passage. Or it may find the time, while the answer states a different one.

00:00:42.250 — A worked example · 2

Check the search results before judging the answer.

Visual description:
Check the search results before judging the answer.

00:00:48.042 — Your turn to think

Should you blame the model when the needed source never reached it? Pause and decide before continuing.

Visual description:
Should you blame the model when the needed source never reached it?
Pause the video if you need more time.

00:01:04.917 — Why this answer works

Not yet. Find whether retrieval or generation failed. If evidence is missing or conflicting, keep that limitation visible.

Visual description:
Not yet. Find whether retrieval or generation failed. If evidence is missing or conflicting, keep that limitation visible.

00:01:16.292 — Check 1

Inspect retrieved source IDs.

Visual description:
Inspect retrieved source IDs.

00:01:21.500 — Check 2

Match answer claims to exact passages.

Visual description:
Match answer claims to exact passages.

00:01:27.208 — Check 3

Do not treat document instructions as permission.

Visual description:
Do not treat document instructions as permission.

00:01:33.167 — 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.