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

Annotations already cover the read-only, idempotent, open-world, non-destructive profile, and the description adds substantial context beyond that: exact cost, payment protocol (x402, eip155:8453), and the key billing nuance that nonexistent packages/versions and failures are not charged. This is precisely the behavioral detail an agent needs before calling a paid tool.

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 sentences, front-loaded with the operation and return payload before the cost/payment detail. Dense but every clause carries real information; the pricing sentence is slightly long but justified for a paid tool.

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?

No output schema exists, and the description compensates by enumerating the returned fields (IDs, CVE aliases, severity, fixed-in versions, license, latest version, publish date, deprecation status, one-line recommendation). Combined with cost and billing rules, an agent has everything needed to call correctly.

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%, so the schema already documents all three parameters including the ecosystem enum and the optional version. The description restates ecosystem support and that version is optional, adding minimal meaning beyond the schema. Baseline 3 is correct.

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 ('returns its known vulnerabilities... license, latest version, publish date and deprecation status') and names the data sources (OSV.dev, deps.dev) and supported ecosystems. No sibling overlap exists, so the agent can identify it immediately.

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?

Explicitly names the timing: 'For coding agents to call before adding or upgrading a dependency,' which is a clear usage context. It stops short of stating when not to use it or naming alternatives, but the sibling set is unrelated, so no routing ambiguity remains.

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