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

Annotations already mark it as read-only, idempotent, and non-destructive. The description adds valuable behavioral details: partial failures degrade gracefully, bundlephobia first measurement may take 5-30s, and sources_failed will list timed-out sources. No contradiction 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 well-structured: purpose first, then behavior details, then failure handling, then limitations. Every sentence adds value. Slightly long but justified by composite nature. Not maximally concise but no fluff.

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?

The description fully explains what the tool returns (summary block with specific fields, advisory detail, links, alternative versions), handles partial failures, and notes ecosystem constraints. No output schema exists, so the description carries the full burden and succeeds.

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 descriptions for both parameters. The description reinforces that scoped packages are accepted (already in schema) and version defaults to latest (already in schema). It does not add additional semantic meaning 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 states a clear, specific verb-resource combination: 'Composite should I add this npm package to my project check in ONE call — fans out across deps.dev and bundlephobia'. It distinguishes from siblings by limiting scope to npm ecosystem and directing other ecosystems to deps.dev:version directly.

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 tells when to use: 'Use whenever an agent asks is X safe / popular / small or what does adding lodash cost me'. Also specifies when not to use: 'NPM ecosystem only in v1; PyPI / Maven / Cargo / Go fall under deps.dev:version directly'.

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