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

The annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is known. The description goes beyond annotations by disclosing latency and failure behavior: 'bundlephobia's first measurement on a new version can take 5-30s; sources_failed will list it if it times out, the rest still returns.' It also describes the return payload in detail, which is essential since there is no output schema. 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 dense but front-loaded with the core purpose, followed by usage, output, and caveats. Every sentence contributes meaningful information (e.g., ecosystem limitation, graceful degradation). It is longer than strictly necessary, but the complexity of the composite tool justifies the length. A shorter version would lose beneficial nuance around failure modes and latency.

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 takes full responsibility for explaining return values, and it does so thoroughly ('summary block (is_latest, license, published_at, advisory_count, bundle_kb_min, bundle_kb_gz, dependency_count, has_esm, tree_shakeable), per-advisory detail, links, and a list of recent alternative versions'). It also covers edge cases (non-npm ecosystems, partial failures, timeouts). This makes the tool fully interpretable and usable, even without a 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 description coverage is 100% (both package and version have detailed descriptions in the schema). The description does not add new parameter-level detail beyond what the schema already states, such as scoped packages and default version behavior. Since the schema fully documents parameters, a baseline score of 3 is appropriate; the description's overall narrative doesn't need to re-explain them.

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 clear, specific verb+resource: 'Composite "should I add this npm package to my project" check in ONE call.' It explicitly distinguishes itself from siblings by listing the data sources (deps.dev, bundlephobia) and the types of questions it answers (safe/popular/small). This unambiguously separates it from the other tools in the sibling list.

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 is provided: 'Use whenever an agent asks "is X safe / popular / small" or "what does adding lodash cost me".' It also states an explicit exclusion and alternative: 'NPM ecosystem only in v1; PyPI / Maven / Cargo / Go fall under deps.dev:version directly.' This covers both positive and negative guidance, making the tool's scope unmistakable.

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