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

Annotations already declare readOnly/openWorld/non-destructive, and the description adds genuinely new behavioral context: return format is PNG, with automatic JPEG fallback above 2.5MB. It omits session-state implications (cookies, page position persisting across calls), but that is documented in the schema.

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?

Two sentences, front-loaded with the decision rules, and every clause earns its place — the format threshold and the sibling routing guidance are both actionable.

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?

An output schema exists, so return-value structure needn't be spelled out, yet the description still flags the PNG/JPEG format detail an agent may care about. Combined with 100% schema coverage and clear annotations, nothing needed to call it correctly is missing.

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%, so both parameters — including the session_id reuse semantics and full_page viewport-vs-scroll behavior — are fully documented in the schema. The description adds nothing parameter-specific, which is the expected baseline here.

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 (visual verification of page state) and immediately names the sibling tools it is not — browser_extract and browser_snapshot — so an agent can route correctly without opening schemas.

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?

Explicitly structured as 'Use for:' (layout, images, charts, CAPTCHA, evidence) and 'Don't use when:' (content/structure needed) with named alternatives and a token-cost rationale. Both the positive and negative conditions are covered.

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