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

Annotations only declare readOnly/openWorld; the description adds substantive behavior the agent otherwise wouldn't know: per-call pricing ($0.002 USDC), the x402 payment path (Base, Solana, Arc), and that failed calls are not charged. It also pre-empts misinterpretation by stating the listing is not a risk score. That is materially more than the annotations provide.

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?

Front-loaded with the resource identity, then mode behavior, then the interpretive caveat and cost. Dense but waste-free. The two modes are packed into one flowing block rather than clearly separated, which slightly hurts scannability.

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?

For a two-parameter read tool with full schema coverage and an output schema, the description covers everything an agent needs: what each mode returns, the interpretability caveat, and the cost/payment mechanics including failure billing. Nothing decision-relevant 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 coverage is 100%, so the baseline is 3, but the description adds semantic meaning: cveId acts as a presence-vs-absence switch that changes the entire response shape, and limit caps the newest additions at 50. It also enumerates the per-CVE fields returned, which clarifies what cveId selects.

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?

Names a specific resource (CISA's Known Exploited Vulnerabilities catalog) and precisely splits behavior into two modes: CVE lookup vs. catalog summary. An agent can tell what it returns in each case. It stops short of naming the relevant siblings (security_cve_nvd_lookup, security_epss_exploit_score) to disambiguate which vulnerability source to pick.

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 'With cveId / Without it' structure gives clear conditional usage for both modes, and the caveat that listing means reported exploitation rather than a risk score is a real usage constraint. No explicit exclusions or alternative-tool routing is provided, so it falls short of a 5.

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