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

The description adds significant behavioral context beyond the annotations: it is a composite call that fans out to two services, it degrades gracefully on partial failures, and bundlephobia's first measurement can take 5-30s, with sources_failed listing timeouts. It also details the exact return block (is_latest, license, etc.), which the annotations do not provide. No contradictions with the readOnly/idempotent hints.

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 description is dense but every sentence earns its place: it covers purpose, usage triggers, return fields, ecosystem scope, and failure behavior. It is well-structured with clear separations, and there is no redundant or filler content. The use of parentheses and lists makes the information scannable.

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?

Despite lacking an output schema, the description lists the exact return fields (summary block, per-advisory detail, links, alternative versions), explains the NPM-only constraint, and describes partial failure behavior. This is complete for a tool of this complexity, and the annotations cover safety and idempotency, so nothing essential 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 parameters are fully documented in the input schema itself. The description does not add significant new meaning beyond what the schema already provides (e.g., 'package' and 'version' are self-explanatory). The description's mention of defaults and scoped packages is already present in the schema, so no extra value.

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 description clearly states the tool is a composite check for 'should I add this npm package to my project', specifying it fans out across deps.dev and bundlephobia. It names specific resources and functions (license, advisories, version history, bundle size, dependency count, ESM/tree-shake support). This distinguishes it from sibling tools that focus on other areas like research or entity profiles.

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 explicitly says 'Use whenever an agent asks "is X safe / popular / small" or "what does adding lodash cost me"', providing concrete triggers for use. It also gives exclusions and alternatives by stating 'NPM ecosystem only in v1' and that other ecosystems 'fall under deps.dev:version directly'. This is clear when-to-use and when-not-to-use guidance.

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