compare_screenshots

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

No annotations are provided, so the description carries full burden. It explains that the tool analyzes pixel differences and returns a text description, including percentage and region of change. It implies no side effects, which is appropriate for a compare tool.

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 description is structured with a clear purpose statement, detailed behavior explanation, bulleted use cases, and parameter list. Every sentence is informative and there is no wasted text.

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 explains what the tool does and returns, but does not detail the exact format of the text description (e.g., coordinates or just percentage). Since an output schema exists, this is acceptable, but a bit more specificity would improve completeness.

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?

With 0% schema description coverage, the description adds meaning for all three parameters: it explains image_path_1 as baseline, image_path_2 as comparison, and max_size as maximum pixel dimension with default 800. This compensates well for the schema's lack of descriptions.

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 clearly states the tool's purpose: 'Compare two screenshots and describe visual differences.' It specifies analyzing pixel differences and reporting percentage of changed pixels and region. This distinguishes it from sibling tools that capture screenshots.

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?

The description provides a bulleted list of useful scenarios (UI changes, visual regression, rendering differences), giving clear context for when to use the tool. However, it does not explicitly mention when not to use it or compare with alternatives.

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