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

No annotations are provided, so the description must carry the safety profile, and it does disclose two meaningful traits: 'Keyless' (no API key/auth needed) and 'read-only' (non-mutating). It stops short of rate-limit or failure-mode detail, but the key operational facts an agent needs are present.

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 tight sentences with the core purpose front-loaded and no redundant restatement of the title. The trailing 'Keyless, read-only' clause earns its place by supplying the missing annotation information compactly.

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 correctly fills the gap by explaining the return values (0–1 probability, 30-day window, percentile rank). Combined with the keyless/read-only note, an agent has everything required to call and interpret this single-parameter 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?

Only one parameter exists and the schema documents it at 100% coverage with a format example ('CVE-2021-44228'), so the schema does the heavy lifting. The description adds interpretive value about what the returned score means but nothing about the input beyond 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?

States a specific verb and resource ('Get a CVE's EPSS score') and immediately defines what that value means (exploitation probability over 30 days plus percentile rank). It explicitly differentiates from the sibling kev_check by framing EPSS as a forward-looking likelihood versus confirmed exploitation.

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?

The phrase 'complements kev_check's confirmed exploitation' gives clear contextual guidance on when this tool is the right pick relative to a named sibling. There is no explicit when-not or prerequisite guidance, but the positioning is unambiguous enough for an agent to route correctly.

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