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

The annotations (readOnlyHint, idempotentHint, destructiveHint: false) already signal a safe read operation. The description adds significant behavioral depth: it fans out across two services, enumerates the return summary fields, discloses partial failure behavior via sources_failed, and warns about the 5-30s latency on bundlephobia's first measurement. No contradiction with 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?

The description is dense yet efficient: each of its five sentences adds a distinct piece of value (composite purpose, usage trigger, return fields, ecosystem scope, failure/latency behavior). No redundant phrasing, and the structure progresses logically from high-level intent to operational caveats.

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 fully enumerating the return fields (is_latest, license, bundle_kb_min, etc.), covering partial failure handling, and specifying the npm-only limitation. It also sets latency expectations. For a composite tool of this complexity, this is a complete and agent-ready spec.

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 has 100% coverage with clear descriptions for both `package` and `version`, including scoped-package syntax. The description adds no new meaning beyond the schema—it mentions using 'lodash' as an example but does not elaborate on the parameters. Baseline 3 is appropriate since the schema carries the semantic weight.

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 is both specific and vivid: it frames the tool as a "Composite ... check in ONE call" and explicitly enumerates the underlying services and checks (license, advisories, bundle size, etc.). It clearly distinguishes from sibling tools by scoping to npm packages and naming the exact data sources.

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 explicitly states when to use the tool: 'Use whenever an agent asks "is X safe / popular / small" or "what does adding lodash cost me".' It also provides an explicit exclusion for non-npm ecosystems: 'PyPI / Maven / Cargo / Go fall under deps.dev:version directly,' which serves as a when-not-to-use and alternative.

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