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

Annotations already declare readOnly, idempotent, non-destructive. The description adds substantial context beyond that: partial failures degrade gracefully, first measurement can take 5-30s, sources_failed lists timeouts, and the return summary block fields are enumerated. This gives the agent a detailed execution model absent from 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?

Though dense, every sentence earns its place: purpose, use cases, return fields, and limitations. It is front-loaded with the core purpose and the structure is logical (purpose → usage → output → caveats). No filler or redundant repetition of schema details.

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?

For a composite tool with no output schema, the description is remarkably complete. It describes the return block, per-advisory details, links, alternative versions, failure modes, timing, and ecosystem exclusions. There is no extraneous dependency on a missing output schema.

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 schema already covers both parameters 100% (package name and version default). The description does not add additional parameter-specific meaning—it focuses on behavior and output. Per the rubric, when schema coverage is high, baseline 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 clearly states a specific verb+resource: 'Composite "should I add this npm package to my project" check in ONE call'. It distinguishes itself from siblings by detailing the fan-out across deps.dev and bundlephobia. The use-cases ('is X safe / popular / small' or 'what does adding lodash cost me') make the purpose 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?

Explicitly provides when-to-use guidance: 'Use whenever an agent asks...'. It also gives a clear exclusion: 'NPM ecosystem only in v1' and points to an alternative for other ecosystems ('PyPI / Maven / Cargo / Go fall under deps.dev:version directly'). Even covers partial failure behavior.

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