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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description goes beyond that by disclosing the underlying paid route (GET /x402/kevcheck) and a price ($0.10), which is real behavioral context an agent needs for cost-aware routing. It stops short of saying what happens on a 402 or what the response shape is, though the payment parameter schema covers the challenge flow.

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 terse clauses, front-loaded with what it does, followed by route and cost. Every token carries information; there is no filler or restatement of the tool name.

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 should say roughly what comes back (e.g., whether the version is listed in KEV, matched CVEs with IDs/severity). It omits that entirely, leaving the agent unsure whether the result is a boolean verdict, a CVE list, or raw feed data. The payment mechanics are fully covered by the parameter schema, so the remaining gap is squarely on the return side.

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%, including a detailed explanation of the payment proof parameter, so the schema carries the load. The description only echoes that software and version are the query inputs via the visible URL template; it adds no format, matching, or edge-case semantics beyond that. Baseline 3 applies.

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+resource: a CVE check for a software+version pair, resolved against CISA KEV and NVD. That is immediately distinguishable from every sibling (DNS checks, Polymarket, weather, SEO audits). It does not explicitly name a sibling alternative, but none of the listed siblings are plausibly confusable.

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?

Usage is only implied: 'for software+version' tells the agent what input shape to bring, and the '$0.10' signals a paid call, but there is no explicit when-to-use, when-not-to-use, or alternative named. The agent must infer that this answers 'is this version vulnerable?' rather than, say, returning a general advisory feed.

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