press_global_action

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

With no annotations, the description carries full behavioral burden. It usefully discloses the prerequisite ('requires the Portal accessibility service to be enabled') and the underlying GLOBAL_ACTION_* semantics, but says nothing about side effects of impactful actions (lock_screen, take_screenshot, power_dialog) or the verify/rollback behavior implied by the schema's verify fields.

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?

Front-loaded with purpose, then the valid action list, then the semantics/requirement note. Every sentence has a role, though the action enumeration duplicates the schema's own list, so it is slightly redundant rather than wasteful.

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 tool with no output schema and no annotations, the description covers the prerequisite and action semantics adequately, but omits what happens on failure (e.g., whether an unsupported action errors, whether lock_screen/take_screenshot have special permission needs), which matters for these system-level actions.

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 description coverage is 100%, so the baseline is 3. The description adds the mapping to Android GLOBAL_ACTION_* constants, which gives real meaning to the action strings beyond the schema's bare enumeration, but adds nothing about the verify parameters.

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?

Names a specific verb and resource ('Performs a system-level action') and enumerates the exact valid actions, which lets an agent distinguish it from siblings like tap, swipe, and keyboard_key. It stops short of explicitly saying it is the navigation/global-action tool rather than the input-simulation tool, but the action list conveys that.

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?

Usage is implied by the action names (home, back, recents are clearly navigation actions), but there is no explicit guidance on when to prefer this over tap/swipe or keyboard_key for navigating the device's UI. No exclusions or prerequisites for choosing this tool are stated.

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