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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint, so the safety profile is clear. The description goes beyond annotations by disclosing partial failure behavior (bundlephobia first measurement can take 5-30s, sources_failed lists timeouts), the non-atomic nature across sources, and the exact return summary fields. This adds significant behavioral context beyond the structured 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 long but information-dense, with a clear progression: purpose, usage triggers, return fields, ecosystem scope, and failure modes. Every sentence contributes unique value for a composite tool. It is not overly verbose given the complexity, though it could be tightened slightly without losing critical 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?

With no output schema, the description carries the full burden of explaining the return payload, and it does so thoroughly: it lists the summary fields, per-advisory details, links, and alternative versions. It also covers timeout behavior, partial failures, and ecosystem limitations. For a tool of this complexity, the description is remarkably complete.

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 description coverage is 100%, with both 'package' and 'version' well-documented in the schema. The description adds marginal value by framing 'version' as optional and defaulting to latest, and by mentioning scoped packages, but this is largely redundant with the schema. The description doesn't add deeper parameter-level semantics beyond the schema, so 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 it is a composite check for 'should I add this npm package' and explicitly lists the data sources (deps.dev, bundlephobia) and the decision context. It distinguishes itself from siblings by being the only npm package evaluation tool, with a specific verb and resource ('scan' + 'dependency').

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 provides explicit trigger conditions ('whenever an agent asks "is X safe / popular / small" or "what does adding lodash cost me"') and also gives an explicit exclusion/alternative for non-NPM ecosystems ('PyPI / Maven / Cargo / Go fall under deps.dev:version directly'). This is excellent guidance for tool selection.

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