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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, openWorld), and the description adds materially different context: the url fetch is server-rendered only with no JavaScript execution, @graph and @id references are followed, and validity is reported separately from rich-result eligibility. These are behavioral traits an agent could not infer from the schema.

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?

Front-loaded with the verb and resource, then output shape, then input-mode guidance. Every sentence earns its place, though the final sentence is dense with stacked parentheticals and could be split for faster scanning.

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 burden of describing returns and does so by naming the two report categories and the covered rich-result types. Combined with fetch semantics and parameter guidance, an agent has enough to call it correctly; only error behavior on unreachable URLs or malformed markup is unaddressed.

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 50% (url carries no schema description), and the description compensates by explaining both parameters: url fetches the live page as the server sends it, html accepts raw HTML or just the ld+json script blocks, including markup from staging servers. This adds real semantics beyond the schema, though it does not cover edge cases such as both being supplied.

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?

Names a specific verb and resource (validate structured data) and immediately scopes it to JSON-LD and microdata with @graph/@id resolution. It further splits the output into two named reports (schema.org validity vs Google rich-result eligibility), so an agent knows exactly what this returns without opening anything else.

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?

Gives explicit conditional guidance for the two input modes: pass url to fetch the live page as served, or html for markup about to be published or fetched from a staging server. There is no explicit 'when not to use this' or pointer to a sibling, but no sibling overlaps, so the mode selection is the guidance that matters.

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