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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and open-world, so the safety profile is covered. The description adds genuinely new context beyond them: output is bounded to "metadata and indicators" and the service "never visits the reported URLs" — an important assurance that no malware is fetched or executed. Pagination, ordering and rate limits are still undisclosed, keeping it below a 5.

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?

Two tight sentences with no filler; the scope-defining clause is front-loaded and the behavioral caveat follows. Every sentence earns its place.

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 no-required-parameter read-only listing tool with no output schema, the description covers what is returned (bounded metadata and indicators) and the temporal window. It falls short only on ordering/pagination and the specific indicator fields, which matter slightly more here because there is no output schema to fall back on.

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% for the single `limit` parameter (default 20, max 100), so the schema already carries the semantics. The description adds nothing about the limit or about ordering/capping of the returned window, 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 ("List"), a precise resource ("recent malware-distribution URLs added to URLhaus") and the exact scope ("rolling three-day window"). This is clearly distinguishable from the sibling urlhaus_lookup_* tools (point lookups) and urlhaus_recent_payloads (payloads rather than URLs) without opening a 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?

Usage is only implied: the rolling three-day window tells an agent this is for fresh, unfiltered threat-intel listings, not for resolving a known URL or host. However, no explicit when-to-use/when-not guidance is given and no alternative (urlhaus_lookup_url, urlhaus_lookup_host, urlhaus_recent_payloads) is named, so the agent must infer the routing itself.

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