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

With no annotations, the description carries the full burden and does so: it discloses deduplication of GHSA vs PYSEC/GO records, that the recommended upgrade is re-checked against OSV, the data sources and their licensing (OSV.dev CC-BY 4.0, deps.dev), the charging model ($0.003 USDC via x402) and that failed/unknown lookups are not charged. That covers cost, side effects and failure modes that structured fields do not.

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?

The purpose is front-loaded in the first sentence and the remainder is grouped logically by return payload, provenance and pricing. The long enumeration of returned fields is dense but justified since there is no output schema; a few items (the trailing '...' ecosystem list, duplicated ecosystem names) are mild redundancy.

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 tool with no output schema and no annotations, the description supplies the return shape in detail, the deduplication rule, the advisory sources, error/charging behavior and the payment requirement. Nothing an agent needs to call it correctly or interpret the result 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 description coverage is 100%, so all four parameters are already documented, and the description's 'omit version' note merely restates the schema default. It adds no new meaning for ecosystem aliasing or include_withdrawn, so the 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?

The first clause names a specific verb and resource — 'Security advisories for one open-source package version' — and the parenthetical ecosystem list pins the exact domain. The 'one package version' scoping implicitly separates it from manifest_audit (whole manifest) and vuln_details (single advisory), so an agent can pick it without opening other schemas.

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?

There is explicit guidance for one parameter ('Omit version to check the latest stable release'), which tells the agent how to do a latest-release sweep. However, it never says when to prefer this over manifest_audit or vuln_details, nor any precondition such as needing to know the ecosystem string first. Usage is implied by the scope statement rather than stated.

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