ai-agent-book/slides/lesson-14.md

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theme	title	info	author	transition	mdc	lineNumbers	monaco	aspectRatio	canvasWidth	layout	class
seriph	Lesson 14 — What Makes a Tool Easy for a Model to Use?	English video course for AI Agents in Depth	Bojie Li	slide-left	true	false	false	16/9	980	cover	cover

Build · Chapter 4 · Tools

What Makes a Tool Easy for a Model to Use?

Capability boundaries, granularity, descriptions, and MCP

Lesson 14 of 42 · 18 minutes · Tool Classification; Universal Principles; MCP; Perception Tools

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Build · Chapter 4 · Tools

Problems this chapter will solve

Lesson 14

What Makes a Tool Easy for a Model to Use?

Lesson 15

How Do You Let an Agent Act Without Letting It Cause Damage?

Lesson 16

When Should an Agent Ask for Help or Delegate?

Lesson 17

How Can a Synchronous Model Live in an Asynchronous World?

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Why this problem matters

Granularity

One broad tool or several composable operations?

Description

The model selects tools from names, schemas, and examples.

Fidelity

Arguments must preserve the user's intended operation.

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Three ideas to keep in view

Perception

Read the world without changing it

Execution

Change state and create consequences

Collaboration

Reach another Agent or human

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The book's visual model

MCP protocol interaction sequence

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Dedicated tool vs. Skill + executor

Dedicated tool

• Clear intent
• Narrow schema
• Many definitions at scale

Skill + executor

• General action surface
• Instructions on demand
• Needs stronger sandboxing

Capability expression is a design choice.

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A schema is an Agent-facing API

{
  "name": "weather",
  "description": "Current observed weather for one place",
  "parameters": {"city": {"type": "string"}},
  "required": ["city"]
}

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Test the claim

4-13 min

Discover and call perception tools

Observe: Tool discovery, typed arguments, truncation, and evidence returned

Demo budget: 3 minutes · one contiguous terminal block

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class: course-terminal

Live demo

Switching to the terminal

$ uv run python chapter4/perception-tools/cli.py demo --offline

Run the command(s), narrate decisions, and point to the observation—not just the output.

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What the evidence supports

Finding 1

Read-only tools are easier to cache, parallelize, and trust.

Finding 2

Descriptions should state scope, provenance, and failure behavior.

Finding 3

MCP standardizes interoperability but not tool quality.

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layout: center

Where the claim stops

Boundary condition

Every third-party server creates a new trust boundary for descriptions, credentials, and returned content.

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layout: center

Engineering takeaway

Design rule

Design tools for faithful action and inspectable evidence before optimizing convenience.

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Continue the experiment

MCP server implementation chapter4/perception-tools/ Container deployment chapter4/DOCKER_DEPLOYMENT.md Tool taxonomy book-en/chapter4.md

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layout: center class: text-center

Pause and apply

Your turn

Which parameter in your tool can silently change the meaning of the user's request?

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layout: center class: text-center

Next · Lesson 15

Add execution power without letting a model become the security boundary.

→