EPSS Score

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

Annotations already establish readOnly, idempotent, openWorld, and non-destructive behavior, so the description only needs to add context. It does add meaningful context: the 0-1 scale, the 30-day forecast horizon, the FIRST.org source, and batch capability. It stops short of noting rate limits or error behavior for unknown 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?

Three compact sentences, front-loaded with the score definition and meaning before the invocation guidance and source attribution. No filler or repetition.

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 and full schema description coverage, the description need not document return values or parameters. It covers purpose, semantics, source, and parameter routing; the only omission is behavior when both parameters are supplied or when CVE ids are unrecognized, which is a minor gap.

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 100%, so the baseline is 3. The description goes slightly beyond the schema by prescribing the routing rule: 'Pass cve_id for one, or cve_ids (array or comma-separated) for many,' which tells the agent which of the two optional parameters to choose in a given situation.

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 ('Get the EPSS exploit-probability score (0-1) and percentile for one or more CVEs') and explains what the number means via the 30-day exploitation window. It does not name a sibling for contrast, but the purpose is unmistakably distinct from cve_lookup, known_exploited, and the dependency tools.

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 it to prioritize patching' gives an intended use case, so usage is implied rather than absent. However, there is no guidance on when to prefer this over known_exploited (confirmed exploitation) or cve_lookup, and no exclusions or prerequisites are stated.

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