apple_tv_screenshot

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

Annotations already declare readOnly/idempotent/non-destructive, yet the description adds real behavioral context beyond them: the capture is a frozen snapshot that can go stale, DRM-protected video may render black while surrounding UI stays visible, and the tool depends on an optional screen-capture helper whose absence is reported rather than silently failing. These are exactly the caveats an agent needs to interpret results.

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?

The primary action is front-loaded in the first sentence, and the following sentences each cover a distinct failure/interpretation case (staleness, DRM black regions, missing helper). It is mildly longer than strictly necessary for a no-argument tool, but no sentence is filler.

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?

Given no output schema, the description carries the return-value burden well by stating the result is a single PNG and by pre-empting the two most likely misreadings (stale capture, black DRM region). It also discloses the helper dependency, so an agent knows what an unavailable-capture response means.

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 and schema coverage is 100%, so per the baseline no parameter guidance is required. The description correctly adds nothing about arguments and instead spends its words on output interpretation.

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?

The first sentence states a specific verb and resource ('Capture the Apple TV screen') plus the output form ('one PNG image'), which is unique among siblings that otherwise control playback, volume, power, or apps. An agent can distinguish it from every sibling without opening 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?

It supplies clear usage context: 'point-in-time evidence of what the Apple TV rendered when the capture ran' and 'capture again to verify' after later actions. It does not name an alternative tool or state when-not to use it, but with no sibling offering similar functionality there is little to exclude.

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