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

Annotations already mark it read-only and idempotent, but the description goes further by disclosing the fan-out behavior across external services, the specific return fields, and the graceful degradation of partial failures. It even mentions a 5-30s latency for first-time bundlephobia measurements and how sources_failed will report timeouts, which is highly valuable beyond the 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 but highly structured, leading with the core composite purpose, then usage, return values, and failure behavior. Every sentence adds value; there is no filler or redundancy. It is appropriately sized for the tool's complexity.

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 there is no output schema, the description fully covers the return format: summary block fields, per-advisory detail, links, and alternative versions. It also explains the partial failure behavior and ecosystem scope. The tool's complexity is well-served by this complete description.

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 and version), so the schema already documents them thoroughly. The description adds no extra parameter-level detail; it mentions npm ecosystem but that's already in the package description. Baseline 3 is appropriate.

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 clearly states what the tool does: a composite 'should I add this npm package' check, fanning out to deps.dev and bundlephobia. It specifies the exact data points (license, advisories, version history, bundle size, dependency count, ESM/tree-shake support), making it distinct from any sibling tool. The purpose is immediately obvious.

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 gives a when-not by stating 'NPM ecosystem only in v1' and directs non-NPM users to 'deps.dev:version directly', offering a clear alternative.

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