Highlight something on screen

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

With no annotations provided, the description must carry the behavioral burden. It discloses 'ephemeral' and 'temporary' to indicate the non-persistent nature of the highlight, but it does not explicitly state that the tool modifies no underlying state or that the highlight fades without side effects. This leaves some room for agent interpretation.

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 consists of two concise sentences. The first imparts the core action and scope, and the second offers a practical usage tip. There is no fluff, and the information is front-loaded, making it easy for an agent to scan and apply.

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?

For a simple drawing tool with no output schema, the description covers the core behavior and usage preference. It could mention the optional duration parameter or its bounds explicitly, but those are already in the input schema. The tool's behavior is sufficiently explained, though there is no clarification about its relationship to sibling manifestation tools, which slightly detracts from 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?

Schema description coverage is 50%; the description parameter is already well documented (with an example), and the tool description aligns with it ('described on-screen content'). However, the description says nothing specific about durationSeconds beyond the schema's default/range, so it does not add meaningful semantic value to that parameter. Since the coverage is exactly at the threshold, the description provides only marginal added insight.

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 it 'Draws a bounded, temporary highlight over the described on-screen content', identifying the specific action and target. However, it does not directly differentiate from sibling tools such as spawnPresence, so it falls short of full 5 for sibling awareness.

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 sentence 'Prefer this over describing a location in text when the user can see their screen' gives a clear context for when to use this tool. It does not mention alternatives like sibling manifestation tools, but the guidance is explicit about a common alternative.

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