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

Annotations already declare read-only, idempotent, and non-destructive. The description adds noteworthy behavioral details beyond that: partial failures degrade gracefully, bundlephobia's first measurement may take 5-30s, and the `sources_failed` field will list timeouts while the rest of the result still returns. This prepares the agent for latency and partial result handling.

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?

Every sentence earns its place: purpose, usage, output fields, ecosystem limitation, and failure behavior are each covered in one dense but efficient paragraph. The most important information (what it does) is front-loaded, and there is no redundant or filler content.

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 takes on the duty of explaining return values. It lists the summary block fields, per-advisory detail, links, and alternative versions. It also covers timeout behavior and partial failure semantics, making the tool's behavior fully predictable for an agent.

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 has 100% description coverage for both parameters: `package` (with scoped package acceptance) and `version` (defaults to latest). The description does not add any new parameter-level semantics, so it gets the baseline score of 3 for a well-documented 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 uses a specific verb ('check') with a clear resource (an npm package) and immediately distinguishes itself from siblings by describing the composite fan-out across deps.dev and bundlephobia. It targets a common agent question ('should I add this npm package') and names the exact data sources, making it unmistakable.

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 triggers are given: 'Use whenever an agent asks "is X safe / popular / small"'. It also provides an exclusion ('NPM ecosystem only in v1') and directs users to an alternative ('PyPI / Maven / Cargo / Go fall under deps.dev:version directly'), giving clear when-to-use and when-not-to-use guidance.

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