add_highlight

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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It only says the highlight is 'semi-transparent' and does not clarify what happens to the image, whether the operation is reversible, how opacity/color interact, or what the output represents. For a mutating image tool, this is a notable gap.

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, efficient sentence with no filler and front-loads the core action. It is concise, though it may be too terse to fully convey behavioral or selection context.

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?

Given the large number of sibling annotation tools and the absence of annotations, the description is incomplete for helping an agent decide when to select this tool. It lacks usage conditions, visual/behavioral details beyond 'semi-transparent', and any mention of how this relates to add_box or precise_annotate. The schema and output schema help, but the description still leaves important context unstated.

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?

The input schema has 100% description coverage, so the parameters are already well documented in the schema. The description adds no additional parameter meaning, which is acceptable under the baseline for full schema coverage, but it does not go beyond it either.

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 clear verb ('Add') and resource ('highlight region to the image'), which conveys the tool's primary function. It is distinguishable from siblings like add_box and add_line by the notion of a 'semi-transparent highlight region', though it does not explicitly contrast with those alternatives.

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 provided about when to use this tool versus the many sibling annotation tools (add_box, add_circle, precise_annotate, etc.). The agent must infer usage from the tool name and short description alone, and there is no mention of exclusions or alternatives.

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