aua_screen

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

Annotations already declare idempotentHint=true and readOnlyHint=false; the description adds meaningful context beyond them by disclosing the transport (H.264 stream), the external ffmpeg dependency, and that calling it reuses an existing panel rather than spawning a new one. It stops short of describing failure behavior if ffmpeg is absent.

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 short sentences with the core action front-loaded and the differentiator and dependency following in priority order. The telegraphic, uppercase 'READY' reference is slightly cryptic but costs no extra length.

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 no-parameter, no-output-schema tool whose main risks are environment prerequisites, the description covers the dependency and the reuse semantics well. It leaves open what the caller receives back (a panel handle or stream reference) and what happens when ffmpeg is missing, which matters for an agent deciding whether it can rely on this tool.

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, so there is nothing for the description to disambiguate; baseline 4 applies. The schema coverage is 100% with an empty object, consistent with the description.

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 concrete verb and resource: 'Open/reuse the Android live screen sidebar.' It implicitly differentiates itself from polling-based siblings by noting it uses 'an independent H.264 video stream, not screenshot/tree polling', but never names aua_screen_frame or aua_observe directly.

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 contrast with screenshot/tree polling, and the 'READY also links the same panel' note hints at a relationship with aua_ready. However, there is no explicit when-to-use statement, no exclusion naming a sibling, and no guidance on when to prefer this over aua_screen_frame.

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