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

Annotations already declare this a safe, idempotent, read-only lookup, so the safety profile is covered. The description adds useful behavior beyond them: it names the returned data sets (KEV, EPSS, CVSS, SSVC, sorted verdict with reasons) and the 20-item batch ceiling, telling the agent this is a batched multi-source lookup rather than a single-record fetch.

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?

Three tight sentences ordered as trigger, input contract, then output, with zero filler. The most decision-relevant clause ('Use this when…') is front-loaded and the example phrasings are compact.

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 no output schema, the description does the work of summarizing the return payload (KEV status, EPSS, CVSS, SSVC, sorted verdict with reasons), and it covers input form and batch limit. The one meaningful gap is the absence of any comparison to the sibling 'recent_kev', which an agent choosing between two KEV-aware tools would benefit from.

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 coverage is 0%, so the description carries the burden, and it delivers something the schema cannot express: the argument accepts raw text containing CVE IDs, not just a clean array of IDs. It also restates the 20-item cap, which is already in the schema. The dual-mode input semantic is the genuinely additive part.

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 states a specific verb and resource ('Check and prioritise CVEs') and enumerates the exact signals it evaluates (CISA KEV, EPSS, CVSS, SSVC) plus a sorted verdict. That is far more than a restatement of the name, but it never distinguishes itself from the sibling 'recent_kev', which also surfaces KEV data, so an agent cannot fully separate the two from 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?

It gives explicit trigger conditions with quotes ('is CVE-… exploited', 'prioritise these CVEs', 'KEV status', 'EPSS score'), which is clear when-to-use guidance. It stops short of stating when NOT to use it or pointing to 'recent_kev' as the alternative for a KEV-feed-style query, so the routing burden remains partly on the agent.

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