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

Annotations already declare readOnlyHint and openWorldHint, so safety is covered, and the description adds genuinely useful context the annotations do not carry: the per-call cost of about $0.0002 and a full inventory of returned data. It stops short of describing failure behavior, timeouts, or whether external fetches are rate limited.

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?

A single front-loaded sentence that leads with the action and resource, then lists outputs, and closes with the cost note in a short separate sentence. Nothing is redundant and no sentence is padding.

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 compensates by enumerating the returned fields thoroughly, which is what an agent needs to decide whether to call it. It leaves out error/timeout behavior and any indication of whether the audit follows redirects, which are the remaining gaps for a fetch-based 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?

Only one parameter exists and schema coverage is 100%, with the schema itself stating the absolute-URL/HTTP(S) requirement, so the baseline of 4 applies. The description adds no format or normalization guidance beyond what the schema already provides.

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?

Uses a specific verb and resource ('Fetches one URL and reports its on-page SEO') and then enumerates exactly what is returned: status code, title, meta description, canonical, headings, word count, link/image counts, load timing and score. The single-URL scope also separates it from bulk/summary siblings such as page_meta or domain_overview.

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?

There is no explicit statement of when to use this versus the closest sibling, page_meta, nor any exclusions such as unsupported schemes, redirect handling, or pages that block bots. The only implicit guidance is the phrase 'one URL', which signals single-page scope but is never framed as a selection rule.

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