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

Annotations already mark readOnlyHint, idempotentHint, and destructiveHint=false. The description adds valuable context beyond that: source (FIRST.org), 6-hour cache, and the exact return format (epss and percentile floats). No contradiction; it complements the annotations by explaining data freshness and scoring semantics.

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?

The description is well-structured with clear sections: purpose, parameter, returns, thresholds, usage guidance, source/cache, and an example. Each sentence contributes useful information and there is no fluff, though it is slightly longer than necessary.

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 annotations covering read-only and idempotent behavior, and an output schema present, the description supplies enough context for an agent: usage guidance, thresholds, source, and cache. It does not mention rate limits or error handling, but these are not critical for a simple read tool.

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?

The input schema covers 100% of the parameter, including a description and example. The description repeats the same example but adds little new meaning beyond what the schema already provides. As coverage is complete, 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 clearly states it retrieves the EPSS exploit probability score for a CVE, predicting likelihood of exploitation. It distinguishes itself from sibling security_fetch_cve_detail by noting that EPSS measures urgency while CVSS measures severity, making its purpose 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?

It explicitly advises using this tool with security_fetch_cve_detail for prioritization and provides actionable thresholds (patch immediately >0.7, patch soon 0.3–0.7, monitor <0.3). This gives clear when-to-use and how-to-interpret guidance, including an alternative tool.

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