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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is covered. The description adds real behavioral context beyond that: it discloses that external resources (robots.txt, XML sitemap) are fetched, that server response time and HTML size are measured, and that the return is a 0-100 score with a fix per issue. Missing are edge behaviors such as what happens for unreachable URLs or how long a check takes.

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 scope and then the checks, with no filler. The check enumeration is long but each item is a distinct signal rather than repetition, so it mostly 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?

There is no output schema, so the description must describe the return, and it does: a 0-100 score plus plain-English fixes. With one fully documented parameter and annotations covering safety, nothing an agent needs in order to call this 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 coverage is 100% and the schema already says 'Public web page' with a concrete example. The description reinforces the single-public-URL constraint, which is modest added meaning rather than new syntax or format detail, 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 ('On-page SEO check of one public URL') and enumerates exactly which signals are inspected. The 'one public URL' scope implicitly separates it from site-wide or bulk siblings like full_site_crawl and bulk_check, so an agent can pick it without opening the 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?

The single-URL, on-page framing gives clear usage context, and the enumerated checks tell the agent what kind of questions this tool answers. It stops short of explicit exclusions or naming the sibling to use for multi-page or bulk work, so the routing is implied rather than stated.

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