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

Goes well beyond the annotations: annotations only say it is non-read-only, open-world, non-idempotent and non-destructive, while the description discloses concrete rate limits (5/IP/hour, 3/session/day), the absence of an API key requirement, the fact that it is asynchronous, and that it returns a scanId requiring polling. Those are exactly the operational facts an agent needs before calling.

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?

Four tight sentences, front-loaded with purpose, then limits, then the return/polling contract, then the upgrade path, and finally a docs pointer. No sentence is filler; each carries a distinct decision-relevant fact.

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, and the description compensates by stating the return value (scanId) and the follow-up call needed to retrieve results. Combined with the rate limits and the anonymous-access condition, nothing material is missing 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?

Only one parameter and schema coverage is 100%, so the schema already documents 'url' with format and an example. The description's phrase 'against a public URL' reinforces the constraint but adds no format, syntax, or validation detail beyond what the schema provides.

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 ('Run a free 6-test HTTP scan against a public URL') with the qualifying constraint 'without an API key'. It also distinguishes itself from siblings by naming guest_get_scan for polling and create_target for monitoring, so an agent can route correctly without opening any 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?

Explicitly gives the when (free, anonymous, one-off scan of a public URL), the alternative (create_target for continuous monitoring), and the follow-up path (poll with guest_get_scan). It also states the exclusion implied by 'public URL' plus the rate-limit ceiling, which tells the agent when this tool will fail.

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