compare_screenshots

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

No annotations are provided, so the description carries the full burden. It transparently states the tool captures screenshots, computes pixel-level diff, and returns both original images plus a diff image. No side effects or constraints are mentioned, but the behavior is well-described.

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 three sentences, front-loading the core action ('Before/after visual comparison with pixel-level diffing') followed by the process and use cases. No redundant or unnecessary 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?

With 4 parameters (2 required) and no output schema, the description adequately covers what the tool does and what it returns (images + diff). It lacks details on output format, but for a visual comparison tool, the explanation is sufficient.

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 coverage is 100% with descriptions for all parameters. The description adds context by labeling urlA and urlB as 'before' and 'after' and providing example values, and explaining width/height as viewport size, adding value beyond the schema.

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 does before/after visual comparison with pixel-level diffing, capturing screenshots of two URLs and returning images plus a diff. It distinguishes from siblings like 'compare_to_baseline' or 'compare_sites' by specifying the exact process.

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 explicitly provides use cases: 'verify UI changes, compare staging vs production, or check before/after states of a redesign.' It lacks explicit when-not-to-use or alternatives, but the context is clear enough for agent selection.

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