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

With no annotations, the description carries the full burden. It discloses rate limits, the lack of an API key requirement, the return of scanId, and the free/guest nature. It does not explicitly state that the scan will send HTTP requests to the target, but this is implied by 'HTTP scan' and 'against a public URL.' Overall, it provides solid behavioral context for a one-off scan tool.

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 description is compact (four sentences) and front-loaded: the first sentence states the core function, followed by rate limits, return value, and an alternative tool. Every sentence earns its place, including the documentation link, with no redundant information.

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?

For a tool with one parameter and no output schema, the description is complete: it explains purpose, rate limits, expected output (scanId), the next step (guest_get_scan), and an alternative for a different use case. The agent has enough context to select and invoke the tool correctly without gaps.

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?

The input schema has full coverage for the single parameter 'url' with a clear description. The tool description adds little beyond the schema, though it reinforces that the URL must be public and supports http(s). Since schema coverage is 100%, the baseline of 3 is appropriate; the description does not meaningfully enhance parameter understanding.

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 clearly states a specific verb and resource: 'Run a free 6-test HTTP scan against a public URL without an API key.' It distinguishes from sibling tools by emphasizing the guest/no-account nature and explicitly mentions scanning a URL, which sets it apart from tools like guest_get_scan (polling) and create_target (continuous monitoring).

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?

The description provides an explicit alternative: 'For continuous monitoring, sign up free and use create_target.' It also directs the user to poll with guest_get_scan, establishing when to use this tool versus follow-up tools. The context of a quick, guest, rate-limited scan is clear, and the exclusion of continuous monitoring is stated.

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