tap

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

With no annotations, the description carries the burden. It discloses the return shape (verification evidence fields), the SELECTOR_AMBIGUOUS case with candidates[], and a retry recommendation. It does not mention side effects or waiting behavior, but the verification result indicates the tool confirms its own action.

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 well-structured: a one-sentence purpose, a bulleted selector guide, and a return-format note. Each component contributes unique value; no filler or redundancy.

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?

Covers the main behavior (verification, ambiguity handling), selector semantics, and output shape. The schema covers device and session_id. It omits potential edge cases like timeouts or post-tap settling, but for a tap tool the description is sufficiently complete alongside the output schema.

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 description adds significant meaning to the target parameter by explaining each 'by' value (text, desc, id, bounds) with examples and a 'last resort' note. This goes beyond the schema's type-only description. session_id is not covered, but schema coverage is moderate and the main required parameter is well documented.

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?

Clear verb+resource: 'tap a semantic target and verify the result.' Distinguishes from sibling tools like swipe/type_text by focusing on semantic selectors and verification. The selector hierarchy (text/desc/id/bounds) further clarifies its scope.

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?

Provides explicit guidance on selector choice: 'Prefer semantic selectors — never compute coordinates yourself,' with a hierarchy (text, desc, id, bounds last resort). Also advises retrying with by=id on ambiguity. However, it does not explicitly compare to alternative tools like swipe or type_text, though the distinct purpose makes this less critical.

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