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

The description adds significant behavioral context beyond the annotations: it explains the composite fan-out into external services, reveals that bundlephobia's first measurement can take 5-30s, and describes graceful degradation with 'sources_failed' listing timeouts while the rest still returns. The positive annotations (readOnly, idempotent) are consistent, and the description enriches the operational 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 somewhat long but every sentence earns its place: it front-loads the core purpose, lists the return fields, and covers failure modes and ecosystem scope. It uses dashes and semicolons for structure, making it scannable despite its length. No word is wasted.

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, the description is remarkably complete: it explains the return summary block fields, per-advisory detail, links, and alternative versions, plus failure behavior and timing. With no output schema provided, the description carries the full burden of return semantics, and it does so thoroughly.

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 input schema already provides 100% coverage for both parameters, including descriptions for 'package' and 'version', and the default for 'version'. The description adds no new parameter-specific meaning beyond that, so it stays at the baseline of 3. It does mention 'npm package' in the purpose, but that's context, not 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 states a clear, specific purpose: a composite 'should I add this npm package to my project' check. It names the exact resources (deps.dev and bundlephobia) and distinguishes itself from any sibling by being the only tool focused on npm package vetting. The verb 'scan' and the comprehensive return list make the scope unmistakable.

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 guidance is provided: 'Use whenever an agent asks "is X safe / popular / small" or "what does adding lodash cost me"'. It also clearly states when NOT to use it, directing non-NPM ecosystems to 'deps.dev:version directly', giving a concrete alternative. This is ideal guidance for an agent deciding between tools.

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