highlight_elements

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

Beyond annotations, the description adds crucial behavioral details: overlays are injected DOM nodes, reload/navigation drops them, and they sit above the page without altering layout or styles. This enriches the agent's understanding of side effects and persistence, fully leveraging the annotation context.

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 concise (3 sentences) and front-loads the core purpose in the first sentence. Each subsequent sentence adds valuable behavioral context without redundancy. Minor improvement would be reordering to place usage context earlier, but overall very effective.

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 no output schema and 6 parameters, the description covers the main behavior, clearing mechanism, and lack of permanence. It does not explain return values, but for a visual feedback tool, this is acceptable. Slightly more context on what happens after highlighting (e.g., can it be removed via remove=true) is already included.

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 schema has 100% coverage with descriptions for all 6 parameters. The tool description does not add new parameter details beyond summarizing the overall behavior, which is appropriate. Baseline 3 is correct as the schema already provides sufficient parameter semantics.

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 outlines every element matching a selector with a coloured overlay, using a specific verb ('outline') and resource ('elements matching a selector'). It distinguishes itself from sibling tools by focusing on visual highlighting for selector verification, not DOM modification.

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 explains when to use the tool: 'to see on a screenshot what a selector actually caught'. It also clarifies call behavior (clears previous overlays) and the effect of remove=true. However, it does not explicitly state when not to use it or compare with alternatives among siblings, slightly lowering the score.

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