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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so safety is covered. The description adds real behavioral nuance beyond them: it fetches and inspects a live page, and it detects the specific case where the counter is installed under a different key. It leaves rate limits and the shape of the answer unstated, keeping it out of 5 territory.

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 sentences, zero filler: the capability and its distinguishing edge case come first, and the when-to-use trigger comes second. Nothing is repeated from the name or schema.

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 two-parameter diagnostic check with annotations supplying the safety profile, the description is nearly sufficient. The one gap is that, with no output schema, it does not say what the answer looks like (a verdict, the detected key, or both), though 'says whether' implies a yes/no result.

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%, so both parameters (key with the osv_ prefix convention, domain) are already documented. The description's mention of a 'different key' scenario gives slight context about how key is used, but adds no syntax or format information beyond the schema. 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 and resource: it inspects a site page and reports whether the OperStack visit counter snippet is present. It goes further by naming the edge case it handles (counter present but under a different key), which separates it from generic siblings like audit_site or ai_visits.

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?

Gives an explicit triggering condition: 'Use it when a counter reports nothing and the owner does not know why.' That is concrete diagnostic guidance. It does not, however, name a when-not condition or route the agent to a specific alternative tool for other failure modes.

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