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

Annotations only declare it is not read-only and not destructive; the description adds real context beyond that by naming the triggering gesture, the panel's contents, and the exact error code returned on unsupported platforms. It does not clarify whether the panel state persists or how the session affects the gesture, leaving a small gap.

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 compact clauses, platform restriction front-loaded, the controls list parenthetical kept tight, and the fallback last. No filler sentences and nothing redundant.

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 single-parameter UI action with no output schema, the description covers the platform constraint, the gesture, the resulting panel contents, and the error path with a sibling alternative. Nothing an agent needs in order to call it correctly is missing.

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% and the single parameter (session, sourced from open_app) is already fully documented in the schema. The description adds no additional meaning about the session parameter, so the baseline 3 applies.

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 resource ("open Control Center") plus the exact gesture ("swipe down from the top right"), and enumerates the controls surfaced. It is immediately distinguishable from siblings like open_notifications or toggle_tile.

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?

Gives an explicit platform condition ("iPhone only") and names the failure mode ("Android fails with no_control_center") along with the alternative to use instead (open_notifications). When-to-use, when-not, and the fallback are all spelled out.

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