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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false. The description adds substantial behavioral context beyond these: partial failures degrade gracefully, bundlephobia's first measurement can take 5-30 seconds, sources_failed will list timeouts, and only the NPM ecosystem is supported in v1. These are non-obvious behaviors that help the agent anticipate side effects and limitations.

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 but well-organized. Each sentence carries meaningful information: the first defines the tool, the second gives usage context, the third lists return fields, the fourth notes ecosystem limits and alternatives, and the fifth explains failure behavior. No fluff or repeated schema content.

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?

There is no output schema, so the description takes on the burden of explaining return values. It lists the summary block fields, per-advisory details, links, and alternatives. It also covers timeout behavior, partial failure handling, and ecosystem constraints. For a composite tool with external service dependencies, this is remarkably complete.

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?

Input schema covers 100% of parameters (package and version) with clear descriptions. The description does not add much extra parameter-specific information beyond what the schema already provides; it only reiterates the npm ecosystem scope. With full 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' that fans out across deps.dev and bundlephobia. It specifies a concrete action, resource (npm packages), and scope (license, advisories, bundle size, etc.), distinguishing it from sibling tools that are narrower or different in focus.

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?

It explicitly says 'Use whenever an agent asks "is X safe / popular / small" or "what does adding lodash cost me"'. It also provides an alternative: 'PyPI / Maven / Cargo / Go fall under deps.dev:version directly', clarifying when not to use this tool and what to use instead. This meets the 'explicit when/when-not/alternatives' criterion.

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