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

Annotations already cover the safety profile (readOnlyHint=false, destructiveHint=false), and the description adds the visual-diff behavior. However, it does not disclose what happens with mismatched sizes, whether uploads are consumed, or what the response contains beyond a direct reading of the parameter descriptions.

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 compact and front-loaded with the core function, followed by a sentence clarifying the required upload names. The only minor redundancy is the 'Image Diff —' prefix mirroring the annotation title, but overall there is no wasted content.

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 plus the rich 100%-covered schema give enough to invoke the tool correctly, and the output_format parameter description explains the returned image and metric headers. Still, the description itself omits practical context such as how normalize affects comparison and what happens if images differ in size.

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 100%, so the schema already documents every parameter. The description only reiterates the names 'image1' and 'image2' without adding new semantic depth, matching the baseline for fully self-documenting schemas.

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 a specific verb and resource: 'Compare two images and highlight the differences visually.' This is sufficient to distinguish it from similarity-analysis or overlay tools in the sibling list, though it does not explicitly name an alternative.

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?

No guidance is given about when to choose this tool over alternatives such as analyze_image_similarity or photo_image_overlay. There are no scenarios, prerequisites, or exclusions stated, leaving the agent to infer appropriate usage.

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