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 useful scope context ('bounded' measurements, the experimental llms.txt signal, and what it explicitly does not measure) but says nothing about auth requirements, rate limits, or cost/latency of the checks.

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?

Three tight sentences, front-loaded with the usage condition, then scope, then exclusions. Every sentence carries distinct information and nothing is repeated from the title or schema.

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?

An output schema exists, so return values need not be explained, and annotations cover the safety contract. The scope statement plus the exclusion list make the tool callable without ambiguity; only minor operational details (rate limits, failure modes on rejected URLs) are absent.

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 description coverage is 100% and both parameters carry their own descriptions (URL constraints, language enum with default), so the baseline of 3 applies. The description adds no syntax, format, or interpretation guidance for url or language beyond what the schema already states.

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?

The description names a specific action ('measures') and enumerates the exact resource surface: page, robots, structured-data, sitemap, and experimental llms.txt signals. The negative list (AI mentions, rank, visibility, firewall passage, sales) further sharpens the boundary so an agent cannot confuse it with a ranking or visibility tool.

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?

It gives an explicit trigger ('Use only when a user asks to inspect a public website') and clear exclusions that tell the agent when this tool is the wrong choice. It does not name a specific alternative tool to route to, but the sibling set is a catalog family, not a direct substitute, so the exclusion list carries the routing intent.

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