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

Annotations already indicate readOnly, idempotent, and non-destructive, but the description adds critical behavioral details: partial failures degrade gracefully, bundlephobia's first measurement can take 5-30s, and a `sources_failed` field lists timed-out sources. It also clarifies ecosystem scope and what the return block contains. No contradictions with annotations.

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 front-loaded with the core purpose and uses just four sentences to convey composite nature, use cases, return values, ecosystem scope, and failure behavior. Every sentence provides distinct value, and the length is justified for a tool with this complexity.

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?

The description fully covers the tool's scope, inputs, outputs (summary block fields, per-advisory detail, links, alternative versions), failure modes, and ecosystem coverage. Since there is no output schema, the description adequately compensates by specifying the return structure.

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% description coverage for both `package` (npm package name, scoped accepted) and `version` (specific version, defaults to latest). The description does not add additional parameter-level syntax beyond the schema, so the baseline of 3 applies.

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 'Composite "should I add this npm package to my project" check in ONE call', clearly identifying the tool as a composite scanner for npm packages. It specifies the two data sources (deps.dev and bundlephobia) and the exact purpose. This distinguishes it from any 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?

Explicitly states when to use: 'Use whenever an agent asks "is X safe / popular / small" or "what does adding lodash cost me"'. Also provides exclusion and alternative: 'NPM ecosystem only in v1; PyPI / Maven / Cargo / Go fall under deps.dev:version directly.' This gives clear when-to and when-not-to guidance.

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