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

The description discloses behavioral traits beyond the annotations. It reveals composite fan-out behavior, partial-failure degradation, and a 5-30s latency for first-time bundlephobia measurements, plus the 'sources_failed' field. The annotations already indicate read-only and idempotent, but the description adds operational context that helps the agent set expectations and handle timeouts gracefully. 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 longer than average but well-structured and information-dense. It starts with a one-sentence purpose, then usage, output fields, ecosystem caveat, and failure behavior. Every sentence earns its place—there is no filler or repetition. It could be slightly trimmed, but the structure and front-loading make it easy to scan.

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 absence of an output schema, the description carries the burden of explaining the return values, which it does thoroughly: summary fields, per-advisory detail, links, and recent alternative versions. It also covers ecosystem scope and partial-failure behavior. Minor gaps include error handling for invalid package names or total source failure, but overall it is complete enough for an agent to effectively use the tool.

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 provides 100% coverage for both parameters: 'package' is described as an npm package name with scoped package support, and 'version' is described as optional defaulting to latest. The description adds little extra parameter-level meaning beyond the schema, though it reinforces the NPM ecosystem scope. Baseline 3 is appropriate because the schema carries the burden.

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, action-oriented statement: "Composite 'should I add this npm package to my project' check in ONE call," clearly identifying the tool as a dependency evaluation scanner. It names the data sources (deps.dev and bundlephobia) and the specific outputs, making its unique purpose unmistakable. The description also differentiates it from broader tools by scoping it to NPM and noting that other ecosystems fall under deps.dev:version directly.

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 guidance is provided: "Use whenever an agent asks 'is X safe / popular / small' or 'what does adding lodash cost me'." It also clearly states when NOT to use it: "NPM ecosystem only in v1; PyPI / Maven / Cargo / Go fall under deps.dev:version directly," pointing to an alternative for non-NPM packages. This gives an agent clear decision criteria and a fallback path.

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