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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and non-destructive behavior. The description adds valuable behavioral context beyond that: it warns about bundlephobia's first measurement taking 5-30s, explains graceful degradation with sources_failed listing timeout sources, and details the response structure (summary block, per-advisory details, links, alternative versions). No contradictions 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 appropriately sized for a composite tool. It is front-loaded with the core purpose, followed by usage, return values, ecosystem scope, and failure behavior. Every sentence adds distinct information; no wasted words.

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?

Given the tool's complexity (composite across two services, multiple output fields, edge cases), the description is highly complete. It covers what the tool does, when to use it, what it returns, ecosystem limitations, latency behavior, and error handling. No critical information is missing even without an 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?

Schema coverage is 100% with both parameters documented. The description does not significantly add parameter-specific semantics beyond what the schema already provides; it contextualizes the 'version' parameter implicitly through the return values. Baseline 3 is appropriate given the high schema coverage.

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 specific verb+resource: a composite 'should I add this npm package' check that fans out across deps.dev and bundlephobia. It clearly lists the aspects covered (license, advisories, bundle size, dependency count, ESM/tree-shake support) and explicitly limits to the NPM ecosystem, distinguishing from a direct deps.dev call for other ecosystems.

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 when-to-use guidance is provided: 'Use whenever an agent asks "is X safe / popular / small" or "what does adding lodash cost me".' For non-NPM ecosystems, it points to 'deps.dev:version directly', offering a clear alternative. This makes it easy for an agent to decide when to select this tool.

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