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

Annotations already declare readOnly, openWorld, idempotent, non-destructive. The description adds crucial behavioral context: it fans out to two external services, it degrades gracefully on partial failures, and bundlephobia's first measurement can take 5-30s and may time out (with sources_failed reporting). This goes beyond the annotations and helps set agent expectations.

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. Each sentence earns its place: purpose, usage trigger, return structure, ecosystem limitation, and failure behavior. It is front-loaded with the most important information and does not waste 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?

No output schema exists, so the description must explain return values. It details the summary block fields (is_latest, license, published_at, advisory_count, bundle_kb_min, bundle_kb_gz, dependency_count, has_esm, tree_shakeable), per-advisory detail, links, and alternative versions. It also covers ecosystem scope and partial failure behavior, making it highly complete for a tool of this complexity.

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%, so baseline is 3. The description does not add meaning beyond the schema for the parameters; it mentions 'npm package' and version history but the schema already documents scoped packages and defaulting behavior. No extra constraints or formats are given, so it neither improves nor degrades the baseline.

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, compound purpose: 'Composite "should I add this npm package to my project" check in ONE call' and lists exact data sources (deps.dev, bundlephobia). This distinguishes it from sibling tools focused on betting, research, or visibility, and uses an action verb ('scan/check') with a clear resource (npm package).

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 trigger is provided: 'Use whenever an agent asks "is X safe / popular / small" or "what does adding lodash cost me"'. It also gives an explicit alternative for non-NPM ecosystems ('PyPI / Maven / Cargo / Go fall under deps.dev:version directly'), clearly indicating when NOT to use this tool.

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