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

Annotations already declare readOnlyHint=true and openWorldHint=true, so safety is covered; the description adds genuinely useful context beyond that: it queries endoflife.date, explains why staleness matters (missed security patches), returns a verdict plus reasons, and discloses the $0.005 x402/credit pricing and free-trial status. It does not describe pagination or caching behavior, and the non-idempotent hint is left unexplained, but for a low-risk read lookup this is solid added context.

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 decision question, then a dense but purposeful checklist of evaluated signals, the scope exclusion, and pricing — every clause carries information. The middle catalog of signals runs long as a single sentence, which slightly hurts scannability but not correctness.

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?

An output schema exists, so return-shape exposition is unnecessary, and the description still conveys the substance of the result (verdict + reasons) and the data sources involved. Annotations cover the safe-read profile. Only minor gaps remain (no mention of latency/caching or error behavior on unknown images).

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% and the single 'image' parameter is documented with concrete examples (node:20-alpine, nginx, bitnami/redis:7.2), so the schema carries the burden. The description implies the tag/repository split matters (mutable tags like latest, tag OS version) but adds no format or syntax detail beyond the schema, 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?

States a specific assessment task on a specific resource ('Should you build on this Docker Hub image?') and enumerates the exact signals checked: official status, deprecation, rebuild recency, mutable tags, pulls, architectures, size, EOL runtime/OS. It also names a sibling domain it is not ('Not a CVE scan'), so an agent can separate it from cve and package-audit without opening 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?

Framed as a pre-build decision question, which gives clear context for when to reach for it, and the 'Not a CVE scan' exclusion actively routes the agent away from this tool for vulnerability questions. It stops short of naming a positive alternative (e.g. cve or package-audit) for those cases, so it is clear context without full alternative routing.

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