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

Annotations already cover read-only/idempotent safety. The description adds valuable behavioral context: partial failure degradation with 5-30s latency on first bundlephobia measurement, a 'sources_failed' field for timeouts, and the fact it fans out across multiple services. These go beyond annotations to set expectations about performance and failure modes.

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 adds essential information: purpose, usage trigger, return structure, ecosystem scope, and failure semantics. No filler or repetition of schema fields. It is front-loaded with the core purpose and flows logically.

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 explains return values including the summary block fields, per-advisory detail, links, alternative versions, and the 'sources_failed' field. It also covers scope (NPM only), service fan-out, and latency caveats, making the tool's behavior well-rounded despite external dependencies.

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% — both parameters are already documented with their names and types. The description adds no new parameter syntax or format details beyond the schema; it reinforces that 'package' is an npm package name but does not exceed baseline value.

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's function: a composite check for 'should I add this npm package to my project', fanning out across deps.dev and bundlephobia. It names the verb 'check', the resource 'npm package', and distinguishes from siblings by specifying the NPM-only scope and directing other ecosystems to deps.dev:version.

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 states when NOT to use it, mentioning that PyPI/Maven/Cargo/Go fall under deps.dev:version directly, which identifies an alternative tool.

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