tap_element

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

Discloses key behavioral traits: 'No scroll-into-view or wait — element must already be visible on screen.' Annotations only have destructiveHint=false, so this adds significant value beyond annotations.

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?

Two sentences with no wasted words, front-loaded with purpose, then constraints, then usage guidance. Extremely concise and well-structured.

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 3 simple parameters and no output schema, the description fully covers what, when, and how to use the tool, including constraints and sibling differentiation.

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 coverage is 100%, but description adds meaning by explaining the OR condition between selector and coordinates, and that coordinates are for screen tap. This reinforces usage beyond schema descriptions.

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 taps a matched element or at coordinates, and distinguishes from the sibling tool 'click_element' by specifying it is for iOS where element.click() is ignored.

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?

Explicitly says 'Use instead of click_element on iOS where element.click() is ignored' and specifies 'Provide selector OR both x and y. Mobile-only.' This provides clear when-to-use and when-not-to-use guidance.

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