ui_diff

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations are absent, so the description carries the full burden. It discloses outputs (summary + outlined image) and explains how threshold tuning ignores animations, but it does not explicitly state that the operation is non-destructive or what happens if the referenced checkpoint does not exist.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The one-sentence purpose is front-loaded, followed by a compact output summary and clearly organized args. Every sentence earns its place with no redundancy.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

The description covers purpose, output, and all parameters. For a diff tool with no output schema or annotations, it is sufficient, though missing details like error handling for missing checkpoints or image format are not addressed.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 0%, and the description fully compensates: label ('which checkpoint'), threshold ('per-channel difference... raise to ignore animations'), max_width ('longest edge of returned image'), and serial ('device serial when several are attached').

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description states a specific verb-resource pair ('Compare the screen... against a checkpoint') and clearly distinguishes itself from sibling tools like ui_checkpoint (checkpoint creation) and screenshot (plain capture).

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

It frames the use case explicitly — 'confirm an edit did what you meant and did not disturb anything else' — which gives clear context. However, it does not name alternatives or state when not to use the tool relative to siblings.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.