ui.back

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

No annotations are provided, so the description carries the full behavioral burden, and it discloses nothing beyond the name's own meaning. There is no mention of what happens when no back stack exists, whether it is a device-level or app-level key, or any side effects/dependencies.

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 short phrase with zero waste and the essential idea front-loaded. It is concise to the point of under-specification, but the dimension rewards economy and there is no filler to cut.

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 trivial zero-parameter tool with no output schema, the description is minimally sufficient to call it correctly. It lacks any failure-mode or interaction context (e.g., behavior at the root screen), leaving clear gaps for an automation agent.

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 tool takes zero parameters, which is the baseline-4 case. There is nothing further a description could clarify about arguments for a no-arg navigation action.

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?

"系统返回键" names a single, recognizable action (triggering the system back key), so the agent can infer the tool's purpose. But it is a bare noun phrase with no verb, no scope, and no differentiation from near-identical siblings like ui.home or input.key, which would also perform device-level navigation.

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 description provides no guidance on when to use this versus ui.home, app.stop, or ui.click, and no conditions or prerequisites. Nothing is misleading, but the agent must infer the entire usage context from the name.

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