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

The description adds substantial behavioral context beyond the readOnly/idempotent annotations: it explains partial failure handling ('Partial failures degrade gracefully'), specific latency behavior ('bundlephobia's first measurement on a new version can take 5-30s'), and the fact that 'sources_failed will list it if it times out'. This transparently sets expectations for response behavior and reliability.

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 yet every clause serves a purpose: purpose, usage, return fields, ecosystem scope, and failure behavior are covered in four well-structured sentences. It front-loads the primary action and avoids fluff or repetition of the tool name.

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?

With no output schema, the description compensates by explicitly listing the exact fields returned ('summary block', 'per-advisory detail', 'links', 'recent alternative versions') and covering edge cases (ecosystem limitation, timeout behavior). This provides a complete mental model for an agent to invoke and interpret the tool without ambiguity.

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% — both 'package' and 'version' have descriptions. The description adds the note that scoped packages are accepted and that version defaults to latest, but these facts are already present in the schema. Thus the description does not add significant new meaning beyond the schema, warranting the baseline score.

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 a specific verb+resource: 'Composite 'should I add this npm package to my project' check in ONE call'. It clearly identifies the tool's function—scanning a dependency across two sources (deps.dev and bundlephobia)—and distinguishes it from sibling research/search tools by its focused scope.

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 context is provided: 'Use whenever an agent asks "is X safe / popular / small" or "what does adding lodash cost me"'. It also states the ecosystem limitation ('NPM ecosystem only in v1') and points to an alternative for other ecosystems ('PyPI / Maven / Cargo / Go fall under deps.dev:version directly'), giving clear when-to-use and when-not-to-use guidance.

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