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 genuinely non-structured context: the hash convention matches Shodan's http.favicon.hash, and results are paginated. It does not disclose result volume or ordering, which keeps it short of 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, front-loaded with the core action and ending on the motivating rationale. The clause enumerating returned fields ('page URL, title and favicon details') is largely redundant since an output schema exists, which is minor waste.

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 an output schema present, return values need not be detailed, and annotations cover safety. The description supplies the hash convention, the pagination behavior, and a use-case rationale, which is sufficient for correct invocation. Missing sibling disambiguation is the only notable shortfall.

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 0%, so the description must carry the load. It does clarify the required mmh3_hash parameter's format and external convention, which the bare 'integer' schema does not. However, page and limit are given no meaning beyond the generic 'paginated' hint, leaving a real gap.

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+resource: 'List scans whose favicon has this mmh3 hash.' The parenthetical tying the hash to Shodan's http.favicon.hash convention sharpens what resource is being queried. It does not, however, distinguish itself from the sibling search_by_favicon, so an agent cannot tell the two apart from the text alone.

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 closing line 'Phishing kits often reuse one favicon across many hosts' implies the investigative use case, which is useful motivation. But there is no explicit when-to-use versus search_by_favicon or get_favicon, and no stated preconditions for obtaining an mmh3 hash in the first place.

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