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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false. The description adds valuable behavioral context beyond those: it fans out to two external services, bundlephobia's first measurement can take 5-30s, partial failures degrade gracefully, and sources_failed will list timed-out sources. This goes well beyond the structured annotations and provides critical operational expectations.

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 dense and front-loaded with the core purpose, followed by usage guidance, return fields, ecosystem limitation, and failure behavior. Every sentence provides distinct information, but it is a long single paragraph rather than a more scannable structure, so it loses one point for conciseness.

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 having no output schema, the description enumerates the returned summary fields, per-advisory details, links, and recent alternative versions. It also covers performance caveats, partial failure behavior, and ecosystem boundaries. This is comprehensive for an agent to decide when to use the tool and what to expect from the response.

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%, so both parameters ('package' and 'version') are fully documented in the input schema. The description does not add new parameter-specific meaning; it mentions the ecosystem and default behavior, but those are already in the schema. With high schema coverage, a baseline of 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 clearly states it is a 'Composite 'should I add this npm package to my project' check in ONE call' and identifies the specific data sources (deps.dev for license/advisories/version history, bundlephobia for bundle size/dependency count/ESM support). It names the resource (npm package) and verb (scan/check), and distinguishes itself from sibling tools by being a specialized dependency evaluation tool with no direct overlap.

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?

Provides explicit trigger conditions: 'Use whenever an agent asks "is X safe / popular / small" or "what does adding lodash cost me"'. Also states an explicit exclusion and alternative: 'NPM ecosystem only in v1; PyPI / Maven / Cargo / Go fall under deps.dev:version directly.' This satisfies the when-to-use and when-not-to-use requirements.

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