When not to use an agent

Learn in five minutes

• Do not use a loop for a form with known fields.
• Do not use a loop where a mistake is hard to undo and nobody is watching.
• Do not use a loop to avoid writing the policy down.
• A fixed script plus one model call can be the whole design.
• The engineering note on agents says to start with the simplest thing that works. Confirm the page.

Looking up a library card by id is a function. Summarizing the card in one sentence can be one model call. Neither needs an open loop.

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Visual

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Delete the loop

1. Draw a loop of four tools.
2. Cross out every tool whose order is fixed.
3. If none remain, delete the loop and write the workflow.
4. If one remains, cap it.

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Quiz

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Ecosystem

Simplest design

The fewest moving parts that meet the done check.

Sisters: Workflows, State machines, Function calling.

The same loop can sit behind chat or a voice turn. The channel does not remove the cap.

MCP is one way to plug tools into that loop. It is the next track.

Config

• Write the goal in one sentence.
• Name the input and the allowed output.
• Save the trace next to the result.

Troubleshooting

• The answer looks fluent and is wrong. Check whether a source passage actually contains the claim.
• The loop never stops. Set a step cap and stop when the tool result repeats.

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