compare_screenshot

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

With no annotations supplied, the description carries the behavioral burden and does disclose key behavior: it captures one frame, compares dimensions and changed-pixel metrics, and can optionally save current and diff outputs. It omits whether the operation is read-only, what permissions are required, and how threshold affects results, leaving meaningful behavioral gaps.

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 a single compact sentence-like statement that front-loads the core comparison behavior and follows with implementation details. Every clause adds useful information, and there is no redundant restatement of the tool name.

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 presence of an output schema reduces the need to describe return values, and the description covers the main comparison workflow and optional file saves. However, for a five-parameter tool with zero schema description coverage, it should explain threshold and max_width to be fully self-contained.

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%, so the description must compensate for five undocumented parameters. It implies baseline_path and the optional save_current_path/save_diff_path usage, but it does not explain max_width or threshold semantics, defaults, or valid ranges, leaving important parameters ambiguous.

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 gives a specific verb and resource: a pixel regression check against a local baseline PNG/JPEG. It also clarifies that it captures one frame and compares dimensions, changed-pixel ratio, and bounds, which distinguishes it from generic screenshot tools. It does not explicitly contrast with the sibling screenshot_annotated, but the purpose is clear.

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 usage context by saying it is useful for Canvas UI verification. However, it does not state when to choose this over related tools such as screenshot_annotated or ui_snapshot, nor does it describe exclusions or prerequisites.

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