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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, open-world), but the description adds substantial behavior beyond them: `url` need not belong to the project's domain and is analyzed fresh, and the `state` field's `unreachable` value signals a failed page fetch that 'is never an error' — critical guidance for interpreting 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?

Front-loaded with purpose and cost/behavioral context; every sentence carries useful signal. The browser-extension aside is slightly verbose but grounds the intended use case, so it 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?

With no output schema, the description does well by disclosing the `state` return field and error semantics, and the cost model. It stops short of naming which on-page metrics are returned, which leaves a modest gap for a metrics-reporting 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?

Schema coverage is 100% so both params are already documented, but the description adds meaning beyond the schema: that `url` accepts any http(s) URL outside the project's own domain and is re-fetched each call, and that `state` must be inspected first — the latter being a return-field hint rather than a param.

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+resource (lightweight on-page metrics for one URL) and explicitly positions it as the 'keyword-free, AI-free sibling' of `get_content_optimizer_report`, so an agent can distinguish it from that sibling without opening either 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?

Names the moment to use it ('ambient per-page checks, e.g. the browser extension's on-page panel') and contrasts the tradeoff against the alternative (no keyword, no AI-gateway charge, no competitor crawl or SERP fetch). The routing condition between this tool and its sibling is explicit.

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