An agent is a loop

Learn in five minutes

• An agent here means the model can choose a tool, see the result, and continue.
• A single call with no tool is not that loop.
• The Anthropic engineering note on building agents is a clear public overview. Confirm it is current.
• A workflow with fixed steps is often enough.
• This lab does not claim a production agent deployment.

If the steps never change, write them down. Call a model only where a step needs language. That is a workflow, and it is a valid design.

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Visual

Diagram SVGDiagram PNGDiagram HTML

Flow SVGFlow PNGFlow HTML

Loop or workflow

1. List three steps: look up a note, draft a reply, stop.
2. If the order never changes, label it a workflow.
3. If the model may skip or repeat a tool, label it a loop and add a cap.

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Quiz

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Ecosystem

Workflow

Steps in an order you wrote down.

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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