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

The description discloses failure behavior and performance characteristics beyond annotations: 'Partial failures degrade gracefully — 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.' This complements annotations (readOnlyHint, idempotentHint) and adds operational context. No contradiction with annotations is present.

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 every sentence contributes: purpose, usage, ecosystem scope, failure handling, and return details. It is front-loaded with the primary purpose, and the follow-up details are logically ordered. No fluff or redundant content.

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 having no output schema, the description enumerates the returned summary block fields, per-advisory details, links, and alternative versions. It also explains timeout behavior. This gives a complete mental model of the tool's behavior and outputs, fitting for a composite tool with multiple data sources.

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' and 'version') with clear descriptions. The tool description adds minimal additional parameter semantics, mainly reinforcing that package is an npm package name and version defaults to latest. Since schema coverage is complete, a baseline score of 3 is appropriate.

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 states a specific composite purpose: 'Composite "should I add this npm package to my project" check in ONE call — fans out across deps.dev and bundlephobia.' It clearly identifies the resource (npm package) and the action (scan/check). It also distinguishes itself from siblings by focusing on npm dependency analysis, while siblings like scan_competitor_ai_presence target different domains.

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 is given: 'Use whenever an agent asks "is X safe / popular / small" or "what does adding lodash cost me".' It also excludes non-NPM ecosystems: 'NPM ecosystem only in v1; PyPI / Maven / Cargo / Go fall under deps.dev:version directly.' This provides clear when-to-use and when-not-to-use guidance.

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