epss

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 bar is low; the description still adds real value by disclosing the one-page-per-call pagination model and by warning that scores are exploitation-probability estimates rather than environment-specific risk. It omits rate limits, result ordering, and behavior on invalid CVE IDs.

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 short sentences, no filler, with the operational constraint (one page, 100 max) front-loaded and the interpretive caveat second. 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?

An output schema exists, so return values needn't be explained, and annotations cover the safety profile. The description supplies the paging model and the score-interpretation caveat, which is most of what an agent needs; only pagination mechanics and alternatives are thin.

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 has to carry parameter meaning and it only partially does: "up to 100 CVEs" maps to cve_ids/maxItems and limit's cap, but offset is never mentioned and pagination semantics are left implicit. The CVE-ID format and bounds come entirely from the schema.

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?

Specific verb ("Fetch") plus resource ("FIRST EPSS page") and scope ("up to 100 CVEs") let an agent immediately tell this is the exploitation-probability scoring source, distinct from the OSV/NVD/KEV siblings that return advisory or catalog data. It stops short of explicitly naming a sibling it should be preferred over, but the resource is unambiguous.

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?

There is no when-to-use or when-not-to-use guidance and no routing to alternatives such as kev_check or nvd_cve. "Fetch one ... page" implies the result is paged but never says how to continue to the next page or when to prefer a single-CVE lookup, so the agent must infer usage.

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