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

Annotations already declare readOnly, openWorld, and non-destructive, so the safety profile is covered; the description adds cost ("Free"), a rate limit ("Rate-limited per IP"), and the fact that the check covers both this service's and the caller's own bot rules. It does not describe the response shape or what happens when robots.txt is unreachable.

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?

The cost and timing cue are front-loaded in two short clauses, then the checks are listed compactly. The middle sentence is long and clause-dense (three engines, three rule sources), but every element carries information the caller needs.

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 does the work of telling the agent roughly what comes back — an allowed/blocked verdict plus a recommended engine — which is the key decision information. Some detail on the response structure or failure modes is missing but not essential for correct invocation.

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%, so both parameters are already documented in structured form. The description restates that user_agent triggers a check of your own bot's rules, which reinforces but does not meaningfully extend the schema, so the baseline 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 (check) and resource (a page/URL) and enumerates exactly what is being checked: robots.txt rules, Content Signals, meta robots, bot checks/sign-in, and required rendering engine. This is clearly distinguishable from siblings like read, extract, or screenshot, which consume the page rather than vet it.

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?

"Before an agent spends money or time on a URL" gives a concrete trigger condition, and the engine-selection clause (plain fetch vs Kitesurf vs Chromium) tells the agent how to act on the result. It stops short of naming sibling tools as alternatives or stating when this check can be skipped.

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