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

Annotations already declare readOnlyHint, idempotentHint, and non-destructive. The description adds valuable behavioral context beyond those: fanned-out calls to multiple external services, graceful degradation on partial failures, bundlephobia's first-measurement delay of 5-30s, and the presence of a sources_failed field. 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 a single dense paragraph but logically structured: composite purpose, data sources, usage trigger, return fields, ecosystem limitation, and error behavior. Every sentence contributes useful information, though it is longer than strictly necessary. It earns a 4 rather than 5 due to length.

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?

This is a complex external-data-fan-out tool with no output schema, so the description must explain return values and edge cases. It does so thoroughly: lists all summary fields, per-advisory detail, links, alternative versions, mentions sources_failed, and explains ecosystem boundaries and timeout behavior. No gaps.

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%, with both 'package' and 'version' already described. The description mentions scoped packages and default-to-latest, which are also in the schema, so it adds no new parameter-level semantics beyond what the schema already provides. Baseline 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 clearly states the tool performs a composite 'should I add this npm package to my project' check, listing specific data sources (deps.dev, bundlephobia) and output fields. The verb 'scan' plus resource 'dependency' is specific, and it distinguishes itself from siblings by being npm-specific and composite.

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 guidance is provided: 'Use whenever an agent asks "is X safe / popular / small" or "what does adding lodash cost me"'. It also states an exclusion: 'NPM ecosystem only in v1; PyPI / Maven / Cargo / Go fall under deps.dev:version directly.' This tells the agent when not to use it and what to use instead.

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