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

Annotations mark the tool as read-only, idempotent, and non-destructive, but the description adds valuable behavioral context beyond that: partial failures degrade gracefully, bundlephobia's first measurement can take 5-30 seconds, and failures are reported via sources_failed while the rest of the data still returns. This discloses latency and failure behavior not captured by annotations.

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 dense single paragraph that front-loads the core purpose and use cases, then covers output fields, ecosystem limits, and failure behavior. Every sentence contributes useful information without redundancy or fluff, making it well-structured and appropriately sized.

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?

With no output schema, the description takes on the burden of explaining return values and does so thoroughly: a summary block with specific fields, per-advisory detail, links, and alternative versions. It also covers timeout behavior and degraded partial results, making the tool's behavior fully understandable for an agent.

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?

The schema already documents both parameters with 100% coverage, so the description adds limited value here. It does clarify that the package parameter is npm-specific and that version defaults to latest, but these are marginal additions over the schema. The baseline of 3 is appropriate for high schema coverage.

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 as a composite "should I add this npm package" check that fans out across deps.dev and bundlephobia, giving a specific verb, resource, and scope. It distinguishes itself from siblings by explicitly limiting v1 to the NPM ecosystem and pointing to deps.dev:version for other ecosystems.

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 gives explicit use cases: 'whenever an agent asks "is X safe / popular / small" or "what does adding lodash cost me"'. It also provides an alternative for non-NPM packages, stating that PyPI/Maven/Cargo/Go fall under deps.dev:version directly, which helps an agent decide 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.