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

Annotations already declare destructiveHint=true, readOnlyHint=false, and openWorldHint=true, so safety is covered. The description adds genuinely new behavior: the call is asynchronous and returns a run id immediately rather than the result, which the annotations do not convey. It does not spell out what on-phone state may be altered, so it stops short of a 5.

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?

Three sentences, each earning its place: purpose first, task-shaping guidance with an example second, and the async/polling workflow third. No redundancy and the most important constraint is front-loaded.

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 two-parameter async dispatch tool with no output schema, the description supplies the remaining essentials: that the return value is a run id, how to retrieve the eventual result, and how to inspect the screen. An agent has everything needed to call it and act on the result.

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 both 'slot' (with its video_live precondition) and 'task' are already fully documented in the schema. The description reinforces the narrow-task expectation for the 'task' parameter but adds no format, syntax, or constraint beyond that, 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 resource: dispatch an on-phone GUI agent for a narrow task on a farm phone. The scope qualifiers ('narrow task', 'on-phone GUI agent') distinguish it from phone-command-tool, phone-control-tool, and run-automation-tool without the agent needing to open a schema.

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 tells the caller to keep tasks specific with a concrete example, names the follow-up tool (get-phone-run-tool) and the condition for using it (poll until success/fail), and routes to phone-snapshot-tool for seeing the screen. When-to-use and how-to-follow-up are both pinned down.

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