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

Annotations already mark the tool as read-only, open-world, idempotent, and non-destructive. The description adds substantial behavioral context: it fans out to two external services, returns a structured summary block with specific fields, per-advisory details, links, and recent alternative versions. It also discloses that bundlephobia's first measurement can take 5-30 seconds and that sources_failed will list timeouts gracefully.

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 well-structured and front-loaded with the core purpose. Each sentence adds value: high-level purpose, details of what is checked, usage examples, ecosystem limitation, and failure behavior. No redundant information.

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 complexity (fans out to two services, returns structured data, handles partial failures), the description covers all necessary aspects: exact return fields (summary block), advisory details, links, recent versions, timing on bundlephobia, and fallback for other ecosystems. Since there is no output schema, the description adequately explains the return format.

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 coverage is 100% with descriptions for both parameters. The description adds value by mentioning that scoped packages (e.g., @types/node) are accepted for the package parameter, and that the version parameter defaults to the latest published version. This extra context justifies a score above the baseline of 3.

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 clearly states the composite check for npm packages, specifying it fans out to deps.dev and bundlephobia for license, advisories, version history, bundle size, dependency count, and ESM/tree-shake support. It distinguishes from siblings by noting the npm ecosystem limitation and fallback for other ecosystems, making the purpose specific and actionable.

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 given: 'Use whenever an agent asks is X safe / popular / small or what does adding lodash cost me.' It also specifies when not to use it (non-npm packages) and points to the alternative fallback (deps.dev:version directly). Partial failure handling is clearly explained.

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