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

Adds significant behavioral context beyond the readOnly/idempotent annotations: it is a composite fan-out call, partial failures degrade gracefully, bundlephobia's first measurement on a new version can take 5–30s, and the sources_failed field will identify timeouts. This level of disclosure is genuinely useful for an agent deciding whether to invoke and how to interpret results.

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 longer than a single line but every sentence earns its place. It is front-loaded with the core purpose, then efficiently covers usage, return fields, ecosystem scope, and failure behavior. There is no redundant text or filler; each clause contributes unique, actionable information.

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 the tool's composite nature and the absence of an output schema, the description fully covers what the agent needs: it lists the exact summary fields, per-advisory detail, links, and alternative versions. It also explains timing risk, graceful degradation, and ecosystem limitations, making the tool self-contained from a documentation standpoint.

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 both parameters (package and version) are already fully described with types and defaults in the input schema. The description reinforces that package is an npm name and version defaults to latest, but adds no new semantics beyond what the schema already provides, matching the baseline of 3.

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 opens with a specific composite check: 'should I add this npm package to my project' and names the exact upstream sources (deps.dev and bundlephobia). This clearly distinguishes it from sibling tools and gives the agent a precise mental model of the tool's action and resource scope.

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 usage triggers are provided: 'Use whenever an agent asks "is X safe / popular / small" or "what does adding lodash cost me"'. It also states a clear exclusion and alternative: non-NPM ecosystems should fall under deps.dev:version directly, giving the agent explicit guidance on when not to use this tool.

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