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

Beyond the idempotent/false annotations, the description reveals important behavior: bundlephobia's first measurement can take 5-30 seconds, partial failures degrade gracefully with a 'sources_failed' list, and the tool returns multiple components (summary, advisories, links, alternatives). 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 a single, dense paragraph that efficiently packs purpose, use cases, output details, limitations, and behavioral notes. While it could benefit from bullet points for readability, every sentence serves a purpose and the critical information is 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?

Despite lacking an output schema, the description enumerates the exact fields returned (is_latest, license, advisory_count, bundle sizes, etc.) and explains partial failure behavior. It covers limitations (NPM only, bundlephobia timeout) and alternate usage for other ecosystems, making it fully self-sufficient.

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 provides 100% coverage for both parameters (package name with scoped syntax, optional version). The description adds no new semantic information beyond what the schema's descriptions already state, so it meets the baseline expectation without additional value.

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's purpose as a composite check for adding npm packages, specifying the exact use case ('should I add this npm package to my project'). It names the specific data sources (deps.dev, bundlephobia) and output elements, distinguishing it from simpler tools by emphasizing it's a single call that combines multiple checks.

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?

The description explicitly states when to use this tool: when an agent asks 'is X safe / popular / small' or 'what does adding lodash cost me'. It also provides clear boundaries by noting that other ecosystems (PyPI, Maven, etc.) are not covered in v1 and should be handled via a different tool ('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.