browser_dom

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

Annotations already declare readOnly, idempotent, non-destructive and non-open-world, yet the description still adds real value: a null result when nothing matches, a ~6 s timeout failure when no preview pane runs, and a refusal-plus-user-grant flow on credential pages. It does not state whether the DOM snapshot is a point-in-time copy or whether the 2000-character truncation is signalled in the payload, so it stops just short of 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?

Front-loaded with the return payload, then usage routing, then prerequisites and failure modes, all in three tight sentences with no filler. Every clause carries information an agent needs before calling.

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?

There is no output schema, so the description carries the full burden of describing return values — and it does: field list, truncation limit, coordinate space (CSS px, viewport-relative), and the null case. Combined with the auth and failure-mode notes, an agent has everything required to call this correctly.

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% and the single 'selector' parameter is fully documented as a CSS selector resolved via document.querySelector with first-match semantics. The description restates the same first-match behaviour and adds nothing parameter-specific, so the baseline 3 applies.

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 ('Inspect one element of the preview') and enumerates exactly what is returned: tag, outerHTML, box, computed styles, as JSON. It also names the sibling boundaries (browser_frame for pictures, browser_eval for anything else), so an agent can distinguish it 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?

Explicit routing: use this to check structure and layout, use browser_frame for a picture, browser_eval for anything else. It also states the prerequisite (preview open with agent access), the failure symptom and timing ('fails after about 6 s with no preview pane running'), and the credential-gated refusal path.

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