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

Annotations already declare readOnlyHint, idempotentHint, and openWorldHint=false, so safety is covered. The description adds genuinely new context beyond that: the content is static reference material rather than live EPSS data, and it enumerates the four subject areas returned, which tells the agent to expect documentation, not scores.

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 with no waste; the 'what it explains' clause comes first and the usage trigger second. Slightly dense enumeration of topics, but everything 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?

With an output schema present, return-value explanation is unnecessary, and the single optional parameter defaulting to 'all' is documented in the schema. The description covers purpose, static nature, and usage timing; only explicit sibling routing is missing.

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% and the enum's own description already explains every topic value ('interpretation: score meaning; models: publishing history...'). The description adds no per-topic semantics beyond that, so the schema carries the load and a baseline 3 is appropriate.

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: it explains EPSS interpretation, model publishing dates, coverage limits, and prioritization policy, and calls itself a 'static reference'. That is clearly differentiated in spirit from the data-returning siblings (epss_get_scores, epss_get_timeseries, epss_prioritize_cves, epss_query_threshold), though none are named explicitly.

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?

'Use this static reference before interpreting missing scores, score movement or probability versus percentile thresholds' gives a concrete trigger condition tied to the sibling tools' outputs. It stops short of stating when not to use it (e.g. 'do not call for live scores'), which keeps it from a 5.

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