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

The description goes well beyond the readOnly/idempotent annotations by disclosing composite fan-out behavior, partial failure degradation ('Partial failures degrade gracefully'), a 5-30s latency on first bundlephobia measurement, and the meaning of 'sources_failed'. It also clarifies the return shape and ecosystem scope, adding significant context beyond the structured 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?

Four dense sentences deliver purpose, use cases, return fields, ecosystem limitations, and failure behavior. Every sentence adds value and the most critical information is front-loaded in the first sentence. No filler or repetition.

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 composite complexity and absence of an output schema, the description compensates exceptionally well. It enumerates the summary block fields (is_latest, license, published_at, advisory_count, bundle_kb_min, bundle_kb_gz, dependency_count, has_esm, tree_shakeable), mentions per-advisory detail, links, alternative versions, and explains timeout behavior. This is a complete picture for an agent to invoke and interpret results.

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 already documents both params fully with descriptions (package name, scoped packages accepted; version defaults to latest). The description does not add meaningful new semantic detail about the parameters themselves, so the schema coverage baseline of 3 applies.

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 composite purpose: 'Composite "should I add this npm package to my project" check in ONE call' and names the two underlying services (deps.dev, bundlephobia). It clearly distinguishes itself from sibling tools by being the only dependency-focused scanner, and lists exactly what it returns.

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 guidance is provided: 'Use whenever an agent asks "is X safe / popular / small" or "what does adding lodash cost me"'. It also gives a clear exclusion rule: 'NPM ecosystem only in v1; PyPI / Maven / Cargo / Go fall under deps.dev:version directly', which directs users to an alternative for non-npm ecosystems.

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