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

Beyond readOnlyHint/openWorldHint, it discloses the details that actually govern invocation: 30-60 s typical runtime, a 90 s wait ceiling, the pending + scanId fallback protocol, 24 h per-host caching with a cached: true field, and a free-tier rate limit of 10 calls per hour per IP. These are exactly the non-obvious traits an agent needs to sequence and retry correctly.

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 core purpose and timing are front-loaded, and nearly every clause carries operative information. It is a long single paragraph, though, and the long comma-separated checklist of scanned signals could be tightened without losing meaning.

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 return-value burden and does so thoroughly: it lists the score categories, the individual metrics, the security/SEO checks, and the pending/cached fields. Combined with timing, retry, and rate-limit details, an agent has everything needed to call this correctly on the first try.

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% and the single url parameter is already well documented (public URL, scheme optional, localhost/private hosts rejected). The description adds only the nuance that the URL is "usually the home page," which is a minor clarification rather than new syntax or constraint information.

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 names a specific verb and resource ("Quick scan of one page") and immediately bounds scope to the single URL passed, typically the home page. It enumerates the concrete outputs (Lighthouse mobile scores, LCP/CLS/TBT, HTTPS/TLS/HSTS, meta tags) and explicitly contrasts itself with audit_website for the whole site, so an agent can distinguish it from siblings without reading any 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 gives explicit when-to-use guidance ("right after a deploy as a smoke check") and names the alternative with the condition that selects it ("use audit_website for the whole site"). It also documents the operational branch: call again with the same URL in 30 s if status is "pending", and notes the 24 h cache so the agent can interpret stale results.

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