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

Annotations already declare readOnlyHint, idempotentHint, and non-destructive. The description adds valuable behavioral context beyond annotations: timing (bundlephobia's first measurement can take 5-30s), graceful partial failure behavior (sources_failed lists timeouts), and the ecosystem scope limitation. This is more than the annotation baseline, though it could mention rate limits or data freshness.

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?

A single dense paragraph, front-loaded with the core composite check, then usage triggers, return fields, and limitations. Every sentence carries unique information (sources, use cases, output summary, failure behavior, ecosystem boundary). Slightly long, but no redundancy; the structure is logical and efficient for the tool's complexity.

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 no output schema, the description fully compensates by enumerating the exact return block (is_latest, license, bundle_kb_min, etc.), advisory details, links, and alternative versions. It also covers multi-source behavior, the 5-30s timing caveat, and how partial failures are reported. No major informational gap remains.

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%: both 'package' and 'version' have meaningful descriptions. The tool description reinforces the package scope (NPM only) and mentions version default indirectly, but does not add substantive parameter-level semantics beyond the schema. Baseline 3 is appropriate for 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 opens with a specific verb-resource pairing: 'Composite should I add this npm package to my project check in ONE call' and names the exact data sources (deps.dev, bundlephobia). It clearly distinguishes itself from sibling tools by focusing on npm dependency scanning with a defined return summary block.

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: 'Use whenever an agent asks "is X safe / popular / small" or "what does adding lodash cost me".' Also provides a clear exclusion: 'NPM ecosystem only in v1; PyPI / Maven / Cargo / Go fall under deps.dev:version directly.' This gives both 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.