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

The annotations already indicate idempotent, read-only, and non-destructive behavior. The description adds significant behavioral context beyond annotations: it explains partial failures ('sources_failed will list it if it times out'), timing expectations ('bundlephobia's first measurement on a new version can take 5-30s'), and the composition of the response (summary block, per-advisory detail, links, alternative versions). 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 well-structured, starting with a concise summary of the composite check and usage notes. It front-loads the main purpose and usage. However, the list of returned fields (is_latest, license, etc.) is somewhat verbose and could be delegated to an output schema if one existed. Overall, the description earns its space but could be slightly trimmed.

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 (two external services, partial failures, rate/timing considerations) and the lack of an output schema, the description covers all essential aspects: it describes the return values, explains graceful degradation, and notes the potential delay for new versions. It is complete for an agent to understand what the tool does and 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?

Input schema coverage is 100%, providing baseline 3. The description adds meaning beyond schema: it explains that the package parameter accepts scoped packages like '@types/node', and that the version parameter defaults to the latest version when omitted. This enhances understanding, though the schema already provides clear descriptions.

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 performs a composite check across deps.dev and bundlephobia for npm packages. It uses the verb 'scan' and specifies the resource ('npm package'), making the purpose unambiguous. The description distinguishes the tool from siblings by noting that other ecosystems are handled by a different tool.

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 states when to use this tool: 'Use whenever an agent asks "is X safe / popular / small" or "what does adding lodash cost me".' It also specifies the ecosystem limitation ('NPM ecosystem only in v1') and directs users to an alternative for other ecosystems ('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.