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

Annotations already convey read-only, idempotent, and non-destructive nature. The description adds valuable behavioral details: partial failures degrade gracefully, bundlephobia's first measurement can take 5-30s, and sources_failed will report timeouts. This enriches transparency beyond 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 moderately detailed yet efficient. It front-loads the composite purpose, then covers usage, output summary, ecosystem scope, and error handling. Every sentence adds value, though slightly longer than minimal.

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 no output schema, the description comprehensively lists return fields (summary block with is_latest, license, bundle sizes, etc.), per-advisory detail, links, and alternative versions. It also covers performance caveats and partial failure handling, making it fully informative for an agent.

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%, so baseline is 3. The description adds useful context: version defaults to latest when omitted, and scoped packages like '@types/node' are accepted. This clarifies behavior beyond the schema.

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 defines the tool as a composite check for evaluating npm packages across deps.dev and bundlephobia, addressing questions like safety, popularity, and size. It explicitly distinguishes itself from sibling tools by noting the npm-only scope and directing other ecosystems to deps.dev:version.

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 usage guidance: 'Use whenever an agent asks "is X safe / popular / small" or "what does adding lodash cost me".' It also clarifies when not to use it (non-npm ecosystems) and suggests an alternative (deps.dev:version).

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