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

Even though annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint, the description adds valuable behavioral context: it fans out to external services, can take 5–30s on first bundlephobia measurement, degrades gracefully with sources_failed, and is scoped to NPM. This goes well beyond the annotation 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 well-structured, front-loading the core value ('Composite... check in ONE call') and then efficiently covering sources, use cases, return fields, constraints, and failure modes. Every sentence adds practical information with no fluff.

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 thoroughly explains the return format: summary block fields, per-advisory detail, links, alternative versions, and partial failure handling. It also covers ecosystem limitations and timing behavior, making the tool fully understandable in context.

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 description coverage is 100%, so the baseline is 3. The description does mention NPM-only scope and that version defaults to latest, but those are already captured in the input schema. It adds no new parameter-level detail beyond the schema.

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 clear, specific purpose: a composite 'should I add this npm package' check. It names the exact data sources (deps.dev and bundlephobia) and what it aggregates (license, advisories, version history, bundle size, dependency count, ESM/tree-shake support), making it highly distinguishable from the sibling tools.

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 explicitly states when to use the tool: 'Use whenever an agent asks "is X safe / popular / small" or "what does adding lodash cost me"'. It also gives exclusions and alternatives—'NPM ecosystem only in v1; PyPI / Maven / Cargo / Go fall under deps.dev:version directly'—and clarifies partial failure behavior.

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