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

Annotations already cover the safety profile (readOnly, openWorld, non-destructive), and the description goes well beyond them: it discloses the $0.009 USDC per-call price, the x402 payment path and supported chains (Base, Solana, Polygon, Arbitrum), which clients pay automatically, and a free sample input. Cost and auth requirements are exactly the behavioral context an agent needs before invoking, and none of it is inferable from structured fields.

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?

Dense, single-paragraph and parenthetical-heavy, but front-loaded with the core purpose and every clause carries information (return fields, modes, parameters, price, example). The payment/sample details could be split out, but nothing is filler.

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 5-parameter tool with no output schema, the description covers the two invocation modes, the return field groups from both upstream sources, the cost/auth mechanism, and a working example. The remaining gap is that with zero required parameters it does not state that at least one of cve_id or package is effectively mandatory.

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 only 40% (package and version have no schema descriptions at all), so the description has to compensate, and it largely does: it marks version as 'recommended', presents the cve_id-vs-package+ecosystem alternatives, and repeats the limit default. It does not explain the ecosystem value set fully beyond examples, and the listed ecosystems (e.g. Debian) do not exactly match the schema's enum-style list.

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 (look up a vulnerability by CVE/GHSA id, or check a package version) and even enumerates what each data source returns (NVD: CVSS/CWE/CISA flag; OSV: affected packages/fixed versions). It is clear and self-contained, but it never distinguishes itself from the sibling package_check, which plausibly overlaps with the package-version mode.

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 description implies two usage modes and how to select between them (cve_id, or package + ecosystem with version recommended), which is useful implied guidance. But it never says when to prefer this tool over sibling alternatives such as package_check, nor any exclusions or prerequisites beyond the payment requirement.

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