Light or dark

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

Annotations declare readOnlyHint=false, idempotentHint=true and destructiveHint=false, so the safety profile is already covered. The description adds genuinely new context: the change is scoped to page rendering rather than the user's real preference, and "auto" restores the prior state, implying the emulation persists until reset. It doesn't say whether the setting survives navigations or whether a reload is needed.

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, front-loaded with the effect and closed with the reset instruction. The middle sentence is motivational rather than operational, but it is brief and directly justifies the tool's existence, so it mostly earns its place.

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 one-enum-parameter tool with annotations and no output schema, the description covers purpose, the reason to use it, and how to revert. The only meaningful omission is persistence/lifetime behavior of the emulated scheme across captures or navigations.

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 schema is a bare three-value enum with 0% description coverage, so the description must carry meaning — and it does for "auto" ("hand it back"), which would otherwise be ambiguous. light and dark are left to be inferred from the opening sentence, which is a minor gap but reasonable for self-evident enum values.

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 description states a concrete effect on a concrete resource: the page is rendered as if the user preferred light or dark, without altering the user's actual preference. That is far more than a restatement of the name, though it never names or contrasts a sibling (e.g. set_viewport) to help an agent pick between page-level emulation tools.

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 a clear use case — dark mode is where contrast regressions hide — and tells the agent how to undo the state with "auto". It stops short of explicit when-not guidance or naming an alternative tool for theme-independent checks.

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