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

Annotations already indicate read-only, idempotent, non-destructive behavior. The description adds meaningful behavioral detail: it fans out across multiple external services, bundlephobia's first measurement can take 5-30s, and partial failures degrade gracefully with a `sources_failed` list. It does not contradict the annotations, and the added latency/failure context goes beyond the structured hints.

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 dense but every sentence carries essential information: what it does, when to use it, what it returns, ecosystem scope, and failure behavior. It is a single block of text but reasonably well-organized; slightly long but justified by the tool's composite nature.

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?

Despite having no output schema, the description lists the exact summary fields, per-advisory detail, links, recent versions, ecosystem limitations, and graceful degradation behavior. For a tool with two simple parameters but a rich response, this description fully equips the agent to understand what will happen.

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 with clear descriptions for both `package` and `version`. The description reinforces the meaning ('npm package name', 'specific version') but adds little beyond the schema, so the baseline score of 3 is appropriate.

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, outcome-oriented purpose: a composite 'should I add this npm package to my project' check. It names the exact data sources (deps.dev and bundlephobia) and the data each provides (license, advisories, version history, bundle size, dependency count, ESM/tree-shake support), clearly distinguishing this from sibling tools that target other domains.

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 'Use whenever an agent asks "is X safe / popular / small" or "what does adding lodash cost me"'. It also provides an exclusion for non-NPM ecosystems, directing those to a direct deps.dev:version path. This is clear, practical guidance on when to invoke this tool versus alternatives.

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