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

Annotations already mark the tool as readOnly, openWorld, idempotent, and non-destructive. The description adds concrete behavioral insight: partial failures degrade gracefully, bundlephobia's first measurement on a new version can take 5-30s, and sources_failed will list timeouts. This goes well beyond the annotations to set accurate expectations.

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 dense with useful information—purpose, usage, output fields, limitations, failure behavior—all in a single paragraph. It front-loads the core purpose. While slightly long, every sentence earns its place with no redundancy. A minor truncation could improve conciseness, but it is well-structured.

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 lists all key output fields (is_latest, license, published_at, advisory_count, bundle_kb_min, bundle_kb_gz, dependency_count, has_esm, tree_shakeable) and explains what happens on partial failure. For a tool that queries two external services with complex behavior, this description is remarkably complete.

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 description coverage is 100% for both parameters (package name and version). The description does not add any new semantic detail beyond what the schema already provides. It mentions scoped packages are accepted, but that is already in the schema description. Baseline 3 is appropriate since the schema carries the load.

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 verb-resource-composite: 'Composite should I add this npm package to my project check in ONE call'. It explicitly states the tool fans out across deps.dev and bundlephobia and returns specific metrics. Among 27 sibling tools, none duplicate this npm ecosystem scanning function, so it is well-distinguished.

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?

The description provides explicit when-to-use guidance: 'Use whenever an agent asks is X safe / popular / small or what does adding lodash cost me'. It also specifies the limitation: 'NPM ecosystem only in v1; PyPI / Maven / Cargo / Go fall under deps.dev:version directly', which effectively tells when NOT to use it and directs to alternatives.

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