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

Annotations already indicate read-only, open-world, idempotent, and non-destructive. The description adds valuable behavioral context: it fans out across two services, returns specific fields, handles partial failures gracefully, and mentions that bundlephobia's first measurement can take 5-30s and may time out (sources_failed listed). No contradictions.

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 single paragraph but efficiently packs essential information. It is front-loaded with the core purpose. A slightly more structured format (e.g., bullet points) could improve readability, but every sentence adds value. It is detailed yet not overly verbose.

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 fully covers return values: summary block fields, per-advisory detail, links, and alternative versions. It also addresses edge cases (partial failures, ecosystem limitations) and provides usage context. The description is comprehensive for a tool of this complexity.

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 has 100% description coverage for both parameters, so baseline is 3. The description adds minimal extra beyond the schema: it implies version defaults to latest (already in schema) and mentions the time-out behavior for the tool, not parameters. No significant enrichment for 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 clearly states the tool performs a composite check for npm packages, combining deps.dev and bundlephobia data to answer questions about safety, popularity, and size. It distinguishes from siblings by explicitly limiting to npm in v1 and directing other ecosystems to a different tool.

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 tells when to use: 'when an agent asks is X safe / popular / small' or 'what does adding lodash cost me'. It also provides explicit exclusions: 'NPM ecosystem only in v1; PyPI / Maven / Cargo / Go fall under deps.dev:version directly.' This offers clear guidance and alternatives.

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