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

The description reveals behavioral traits beyond the annotations: it fans out to two external services, bundlephobia's first measurement can take 5-30 seconds, and partial failures degrade gracefully with sources_failed listing timed-out components. These details are not present in the annotations or schema, enhancing the agent's ability to anticipate runtime behavior.

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 compact and well-structured, with each sentence serving a distinct purpose: composite function, usage triggers, return fields, and limitations/failure behavior. There is no filler or redundancy, maintaining high information density without bloat.

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 the summary block fields, auxiliary outputs (per-advisory detail, links, alternative versions), and error handling behavior. It also covers ecosystem limitations and performance caveats, making it fully contextual for a complex composite 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?

The input schema already covers both parameters (package name and version) with clear descriptions, so the schema coverage is 100%. The description only restates the version default and does not add extra semantic detail beyond the schema, meriting the baseline score of 3.

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 states a clear, specific purpose: a composite 'should I add this npm package to my project' check in one call, and names the two upstream services (deps.dev and bundlephobia) with their respective contributions. This goes beyond the generic title and makes the tool's uniqueness obvious relative to 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?

It gives explicit trigger phrases: 'Use whenever an agent asks "is X safe / popular / small" or "what does adding lodash cost me"'. It also provides an exclusion rule for non-NPM ecosystems (PyPI/Maven/Cargo/Go), directing them to deps.dev:version directly, which is excellent alternative guidance.

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