---
title: "Name context, tools, model, guardrail"
lesson_id: "02"
---

# Name context, tools, model, guardrail

- **Lesson ID:** 02
- **Goal:** Name four hops: context pack, tool call, model, and guardrail. State what each one times.
- **Human lesson:** [02-name-the-hops.html](02-name-the-hops.html)

## Prerequisites

- Lesson 01, or the one-call-is-many-hops idea.

## Inputs, outputs, and artifacts

- **Inputs:** The four hop names.
- **Outputs:** A table the team can reuse.
- **Artifacts:** Progressive `.flow` diagrams, a table, and a Swift hop enum.

## Agent build steps

1. Introduce the four names in order with growing flows.
2. Show the four hop names as a Swift enum used around session.respond.
3. Fill the table with time and failure mode.
4. Separate Apple inference from the product guardrail.
5. Link the prompt registry course.

## Constraints

Keep the language simple, friendly, and literal. iOS 27 and macOS 27 only. No quizzes, Mermaid, or em dashes. Do not invent API names. Mark sketches as sketches and tell the reader to confirm them in the Xcode 27 SDK.

## Key concepts

- The four hops in order are context pack, tool call, model, and guardrail.
- Context pack includes instructions, attachments, history, and `historyTransform`.
- Tool call includes Apple system tools and your tools.
- Prompt version and profile name go on the request, not in hop names.

## Takeaways

- Use the same four hop names in every feature.
- Put prompt version and profile name on request attributes.
- Dynamic Instructions and history work belong in context pack.

## Acceptance checks

- All four hops are named.
- Guardrail is marked as product code.
- Sibling links, progressive `.flow` diagrams, and an Agent brief link are present.
- [ ] Proceed to [lesson 03 brief](03-instruments-template.llms.md).