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

The description is unusually rich on behavior beyond the annotations: it discloses the exact return shape, the 3-credit price per successful call, that schema-invalid input is rejected before billing, and (via the schema) that private/internal hosts are refused. However, it contradicts the openWorldHint=false annotation, since auditing 'a live page' at an arbitrary public http(s) URL is by definition open-world interaction; the annotation should be true.

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?

Purpose is front-loaded in the first clause, followed by inspection scope, return shape, and pricing in descending priority. The inline return-key list is long but justified because no output schema exists; a slightly tighter phrasing of the pricing clause would earn a 5.

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 carries the return contract itself and does so concretely (url, status, score, checks with id/pass/weight). Combined with the cost model and the fail-before-billing rule, an agent has everything needed to decide to call it and to interpret the result; the only gap is the mis-set openWorldHint.

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?

There is a single parameter at 100% schema coverage, and the schema already documents the http(s)-only, public-host constraint. The description adds nothing parameter-specific beyond the phrase 'live page', so the baseline of 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 ('Audits a live page') and enumerates exactly what is inspected (title/description length, H1s, canonical, robots, lang, viewport, image alts, structured data, links) with a 0-100 score. That enumerated scope distinguishes it from nearby siblings such as robots-check or header-audit, which each cover only one of these signals.

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?

Usage is only implied by 'audits a live page' and the schema constraint on public URLs; there is no explicit statement of when to pick this over robots-check, header-audit, og-preview or page-markdown, nor any when-not guidance. The billing and pre-billing rejection note does tell the agent the call costs 3 credits only on success, which is useful context but not usage guidance per se.

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