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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It only says it presses a button; it never mentions the implicit re-observation of UI state, the requirement of an active connection, or side effects of navigating back. The observe/settleMs parameters hint at behavior but the description itself adds nothing beyond the action verb.

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?

A single front-loaded sentence with zero padding; the action verb comes first and the qualifier is parenthetical. Nothing is wasted.

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 action tool with no output schema and fully documented parameters, the description is minimally adequate but leaves out the connection prerequisite and the implicit post-action UI observation behavior. It is enough to call the tool, but thin on context.

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?

All three parameters have 100% schema description coverage, so the schema already documents observe, settleMs, and includeScreenshot fully. The description adds no parameter-level meaning, making the baseline 3 appropriate.

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?

States a specific verb and target ('Press BACK'), which is unambiguous as an action on the device's back button. The parenthetical ties it to sibling phone_key as a specialized shortcut, giving partial sibling differentiation, though it never explicitly distinguishes from phone_home or explains what 'BACK' means in navigation terms.

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 'convenience wrapper around phone_key' note gives clear routing context: use this shortcut for the back action rather than configuring phone_key directly. It names the alternative but offers no explicit when-not conditions or prerequisites (e.g., a connected device).

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