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

The description discloses important behavioral traits beyond the annotations: composite nature, graceful degradation on partial failures, potential 5-30s latency for bundlephobia's first measurement, and the sources_failed field to indicate timeouts. It also lists the exact return fields, giving the agent a clear picture of what to expect.

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 but each sentence earns its place: purpose, use cases, return fields, ecosystem limitations, and failure behavior. It is front-loaded with the core purpose. Slightly long but justified given 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?

Without an output schema, the description takes on the burden of explaining return values (summary block fields, per-advisory detail, links, alternatives). It also covers ecosystem scope, partial failures, and latency. The description is comprehensive for an agent to decide to use the tool and interpret results.

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: 'package' is described as an npm package name and 'version' as a specific version with a default. The description adds little beyond that—it mentions the package in the context of npm but does not introduce new semantic meaning for the parameters themselves.

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: a composite 'should I add this npm package to my project' check that fans out to deps.dev and bundlephobia. It specifies the exact resources (npm package, license, advisories, bundle size) and distinguishes itself from sibling tools, which are unrelated to dependency scanning.

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"'. It also provides exclusions and alternatives, noting that non-NPM ecosystems fall under deps.dev:version directly. This is clear guidance on when to invoke the tool versus alternatives.

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