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

Goes well beyond the readOnly/openWorld annotations: it discloses the live-fetch behavior, the 300 KB truncation, the pass/warn/fail result shape, and a prompt-injection warning about untrusted page text. Those are operational facts an agent cannot get from the annotations.

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 and default are front-loaded, and the security warning plus sibling routing land at the end where they belong. The middle is a single semicolon-chained sentence that is dense enough to be harder to scan than a short list, but almost no content is wasted.

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 still explains the return shape (pass/warn/fail with plain findings), the fetch limit, and every check category. 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 already 100%, yet the description still defines what each enum value actually inspects (meta_tags = title/description lengths, robots, viewport, OG/Twitter; canonical = resolution, self-reference, host mismatch, duplicates, hreflang; etc.). That is real meaning beyond the bare enum labels.

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?

Opens with a concrete verb+resource ('On-page SEO and content checks of ANY public web page'), scopes it to live fetches with a 300 KB limit, and enumerates the exact check categories. It also explicitly distinguishes itself from get_site_health, so an agent can pick it over siblings 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?

States the scope (any public page, default check=all) and routes the agent elsewhere for a specific case: 'For an account site's homepage get_site_health already holds the daily SEO and mixed-content audit.' This is explicit when-to-use/when-to-use-something-else guidance.

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