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

Annotations already provide readOnlyHint, idempotentHint, and openWorldHint, establishing safety. The description adds critical behavioral details: partial failures degrade gracefully, bundlephobia's first measurement can take 5-30s, and sources_failed will list timeouts. This goes beyond annotations by explaining failure modes and latency.

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 dense paragraph, front-loaded with purpose. Every sentence adds value: usage, return structure, ecosystem scope, failure handling. It is somewhat long but justified by the tool's complexity. Could be slightly more structured (e.g., bullet points) but still effective.

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 lacking an output schema, the description enumerates all return fields: summary block, per-advisory detail, links, recent alternatives, and sources_failed. It covers ecosystem constraints, partial failure behavior, and latency considerations. This is a very complete description for a complex tool.

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 coverage is 100% with descriptions for both parameters. The description adds extra context: package accepts scoped packages (e.g., '@types/node'), and version defaults to latest. This provides clarity beyond the schema's own descriptions, though the schema already does a good job.

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 starts with a clear, specific verb phrase: 'Composite "should I add this npm package to my project" check in ONE call', which explicitly states the tool's purpose and resource. It distinguishes itself from sibling tools by focusing on npm dependency evaluation across multiple data sources, a unique combination among the listed siblings.

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 clearly states boundaries: 'NPM ecosystem only in v1; PyPI / Maven / Cargo / Go fall under deps.dev:version directly', telling the agent when not to use this tool and what alternative exists.

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