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

Annotations already indicate safe read-only, idempotent, open-world behavior. The description adds significant behavioral context: partial failures degrade gracefully, bundlephobia's first measurement can take 5-30s, and sources_failed reports timeouts. This goes beyond the annotations and sets accurate expectations.

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 fairly long but every sentence serves a purpose: it front-loads the core purpose, then usage context, then output fields, then limitations. It could be tightened slightly by removing some redundancy, but for a complex multi-source tool it remains well-structured.

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?

Given no output schema, the description compensates by enumerating the summary block fields (is_latest, license, published_at, etc.) and mentioning links and alternative versions. It also covers the NPM-only scope, partial failure behavior, and timeout characteristics, making it complete for the tool's complexity.

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 baseline is 3. The description reinforces that the package parameter is an npm package name and that version defaults to latest, but these are already in the schema. It adds the ecosystem limitation (NPM only), but that's more a behavioral note than parameter semantics.

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 identifies the tool as a composite 'should I add this npm package' check, combining deps.dev and bundlephobia data. This specific verb+resource focus uniquely distinguishes it from all sibling tools, none of which serve a similar purpose.

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 states when to use: whenever an agent asks 'is X safe / popular / small' or 'what does adding lodash cost me'. Also gives a clear fallback for non-NPM ecosystems (PyPI/Maven/Cargo/Go), effectively providing a when-not-to-use guideline for those cases.

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