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

Annotations already declare the tool as read-only, idempotent, and non-destructive. The description adds significant behavioral context: it fans out to two external services, returns a specific block of data, and degrades gracefully on partial failures with sources_failed field. It also warns about bundlephobia's slow initial measurement. No contradiction 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 a single paragraph that is front-loaded with the core purpose. Every sentence adds value, including usage guidelines, limitations, and return details. There is no wasted text; it is concise yet comprehensive.

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 fully covers the return structure: a summary block with fields (is_latest, license, etc.), per-advisory details, links, and recent alternative versions. It also explains partial failure handling. This provides sufficient context for an agent to understand what to expect.

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%, but the description adds meaning beyond the schema: it confirms scoped packages (e.g. '@types/node') are accepted for the 'package' parameter, and clarifies that 'version' defaults to the latest published version when omitted. This provides useful semantic guidance for the agent.

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 tool's purpose: a composite check for deciding whether to add an npm package, combining data from deps.dev and bundlephobia. It uses a specific verb ('scan') and resource ('dependency') and distinguishes itself from any sibling tools by specifying the npm ecosystem and the combined sources.

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?

The description explicitly says when to use: for questions like 'is X safe/popular/small' or 'what does adding lodash cost me'. It also notes limitations: NPM only in v1, with alternatives for other ecosystems (PyPI, Maven, etc.) mentioned. Additionally, it explains partial failure behavior and timing expectations (5-30s for bundlephobia first measurement).

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