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

The description adds significant behavioral context beyond the annotations: it discloses that the tool fans out to multiple sources, that partial failures degrade gracefully, that bundlephobia's first measurement on a new version can take 5–30 seconds, and that sources_failed will list timeouts. This is valuable and does not contradict the readOnlyHint=true annotation.

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 earns its place: main purpose, usage triggers, return summary, ecosystem scope, and failure behavior. It is front-loaded with the core function and structured logically, making it easy to scan.

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 enumerates the summary block fields, per-advisory detail, links, and alternative versions. It also covers ecosystem limitations and partial failure behavior, providing a complete picture for an agent to use the tool effectively.

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, describing 'package' as an npm package name with scoped package support and 'version' with default behavior. The description reinforces these but adds no new parameter-level semantic details beyond what the schema offers, 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 clearly identifies the tool as a composite check for npm packages, combining deps.dev and bundlephobia data. It specifies the verb ('check'), resource ('npm package'), and the exact outputs, distinguishing it from all sibling tools, none of which cover dependency scanning.

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 gives a direct alternative for non-NPM ecosystems: 'PyPI / Maven / Cargo / Go fall under deps.dev:version directly', which is a clear exclusion.

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