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

Annotations already declare read-only and idempotent behavior, but the description adds substantial context: fans out across multiple services, returns a specific summary block with enumerated fields, and discloses partial failure/degradation behavior including latency (5-30s) and the sources_failed field. This goes well 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 front-loaded with the core purpose and then systematically covers sources, usage, return fields, scope limit, and failure behavior. It is slightly long but every sentence carries information—no filler. The use of dashes and lists within a single paragraph makes it scannable, though a touch more structure (e.g. separate sentences for each concern) could improve readability.

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 complexity of a composite tool with two external data sources and no output schema, the description is remarkably complete. It details the returned summary fields, per-advisory detail, links, alternative versions, ecosystem limitations, and graceful degradation on partial failures. Agents will know exactly what to expect and how to handle edge cases.

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?

The input schema already fully describes both parameters (package name with scoped package support, version with default-to-latest). The description adds little new parameter-specific meaning beyond what the schema provides, so the baseline of 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 a specific composite check ('should I add this npm package to my project') and names the exact sources (deps.dev, bundlephobia). It distinguishes itself by saying 'in ONE call' and explicitly noting the NPM-only scope, differentiating from other tools.

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?

Provides explicit trigger phrases ('is X safe / popular / small', 'what does adding lodash cost me') and clear exclusion criteria ('NPM ecosystem only in v1; PyPI/Maven/Cargo/Go fall under deps.dev:version directly'). This gives agents concrete 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.