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

The description goes well beyond the readOnlyHint/idempotentHint annotations by disclosing that the tool calls external APIs, explains graceful degradation of partial failures, warns that first bundlephobia measurement can take 5-30s, and mentions the sources_failed field. This gives the agent rich behavioral context without contradicting 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 dense but well-organized: purpose first, use cases, return structure, ecosystem scope, and failure behavior. Every sentence carries important information, with no fluff. It's a bit long, but the complexity of the tool justifies the 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?

Given the tool's complexity (multiple external sources, return summary block, partial failure handling), the description covers all critical aspects: what it fans out to, what fields are returned, ecosystem limitations, and operational caveats. Even without an output schema, the description lists the summary block fields, making the return format clear.

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%, so description doesn't need to elaborate much. It does add the semantic context that the package must be an npm package and that version is optional (defaulting to latest in schema), but this is already present in the schema. No significant extra meaning is added over the schema's parameter descriptions, 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 immediately states the tool's exact purpose: a composite 'should I add this npm package to my project' check that fans out to deps.dev and bundlephobia. It lists specific data points (license, advisories, version history, bundle size, tree-shake support), clearly distinguishing it from sibling tools that focus on markets or AI presence.

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?

Explicitly states when to use: whenever an agent asks 'is X safe / popular / small' or 'what does adding lodash cost me'. Even provides an exclusion: non-NPM ecosystems (PyPI/Maven/Cargo/Go) should fall under deps.dev:version directly, guiding agents to alternatives.

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