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

While annotations already declare readOnly/idempotent, the description adds valuable behavioral context: partial failures degrade gracefully, bundlephobia's first measurement can take 5-30s, and sources_failed will list timeouts. It also explains the fan-out nature and return structure, exceeding annotation coverage.

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 moderately long but every sentence provides unique, essential information: composite behavior, use cases, return fields, ecosystem limitation, and failure handling. No fluff or redundancy; well-structured and front-loaded.

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?

For a composite tool with no output schema, the description is remarkably complete. It explains the exact return fields, latency behavior, ecosystem scope, and graceful degradation. No significant gaps remain given the complexity and available annotations.

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% with both parameters having clear descriptions. The description reinforces the 'latest published version' default but adds no new meaning beyond the schema. Baseline 3 is appropriate given full schema coverage.

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 is a composite check for 'should I add this npm package to my project' in one call, specifying it fans out to deps.dev and bundlephobia. It distinguishes from siblings by explicitly limiting to NPM ecosystem in v1 and noting alternative tools for other ecosystems.

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 given: 'Use whenever an agent asks "is X safe / popular / small" or "what does adding lodash cost me"'. It also provides exclusion guidance for non-NPM ecosystems and describes degrade behavior, making it clear when to use this tool versus deps.dev directly.

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