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

Annotations already indicate read-only, idempotent, open-world, non-destructive behavior. The description adds critical behavioral context beyond annotations: the composite fan-out across two services, partial failure degradation, the 5-30s latency for first bundlephobia measurement, and the sources_failed output. No contradiction with annotations; in fact, it enriches them.

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 a single dense paragraph but front-loaded with the core purpose and usage. It lists output fields and failure modes without unnecessary fluff. Slightly lengthy due to the output field list, but each clause earns its place. Could be broken into bullets, but structure is acceptable.

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 composite tool with no output schema, the description is remarkably complete: input, output fields, ecosystem scope, failure behavior, latency notes, and when to use alternative tools. It covers all aspects an agent needs to invoke and interpret the result correctly. No gaps identified.

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% for both parameters (package and version), so the heavy lifting is done by the schema. The description reinforces version defaults indirectly via the output block (is_latest, alternative versions) but does not add new parameter-level meaning beyond what the schema already states. 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 description states a specific verb+resource: a composite check for 'should I add this npm package to my project', clearly distinguishing it from sibling scan tools by focusing on npm dependency evaluation via deps.dev and bundlephobia. The scope (NPM ecosystem in v1) further differentiates it.

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?

Explicit when-to-use guidance is given: 'Use whenever an agent asks "is X safe / popular / small" or "what does adding lodash cost me"'. It also provides an exclusion: non-NPM ecosystems should use deps.dev:version directly, naming the alternative. This fully addresses usage context.

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