Tap annotated element

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

The annotation readOnlyHint=true contradicts the described action of tapping, which can mutate app state. The description adds useful detail about scaling and stale mappings, but the contradiction with the annotation is a serious inconsistency, forcing a low score.

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 three sentences with no redundancy. Each sentence adds value: purpose, scaling correctness, and staleness warning. It is appropriately sized and front-loaded.

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 two-parameter tool, the description explains the essential behavior, mapping exactness, and the need to re-capture. It doesn't cover error cases or return values, but no output schema exists, so this is adequate. The annotation contradiction is not accounted for here but is penalized under transparency.

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 descriptions cover both parameters, so the baseline is 3. The description adds context about element numbers coming from a recent screenshot and going stale, but this is marginal beyond what the schema already states ('Element number from the annotated screenshot').

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 'Tap element #N from the most recent screenshot', combining a specific verb (tap) with a specific resource (annotated element). It distinguishes from sibling 'tap' by noting 'no coordinate math needed', making the purpose unambiguous.

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 implies usage when an annotated screenshot exists and coordinates are undesirable, and explicitly warns to re-capture after UI changes because element numbers go stale. It doesn't name alternative tools explicitly, but the context is clear and provides actionable guidance.

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