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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false. The description adds substantial behavioral context beyond these: it is a composite tool that fans out to two services, it handles partial failures gracefully, bundlephobia's first measurement can take 5-30s, and sources_failed will report timeouts. It also details what the return payload includes. This adds significant value beyond the structured 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 dense but every sentence earns its place. It front-loads the core purpose, then lists the data sources, usage triggers, output structure, ecosystem limitation, and failure behavior. There is no redundant content, and the structure is logical. The length is justified by the complexity of a composite tool.

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?

The tool has no output schema, so the description carries the full burden of explaining what is returned. It explicitly lists the summary block fields, per-advisory detail, links, and alternative versions. It also covers timing risks, partial failures, and ecosystem scope. Given the tool's complexity, this description is complete and sufficient for an agent to invoke it correctly.

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 clear descriptions in the input schema. The tool description doesn't add any additional parameter semantics beyond what the schema already documents, so the baseline of 3 is appropriate. It doesn't hinder understanding, but it also doesn't enrich the parameter meaning.

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 check for 'should I add this npm package to my project', fanning out to deps.dev and bundlephobia. It specifies the exact inputs (npm package) and distinguishes itself from alternatives by noting NPM-only support and pointing to deps.dev directly for other ecosystems. The verb 'scan' and resource 'dependency' are well-defined and specific.

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 provides usage guidance: 'Use whenever an agent asks "is X safe / popular / small" or "what does adding lodash cost me"'. It also clearly states the limitation and alternative: 'NPM ecosystem only in v1; PyPI / Maven / Cargo / Go fall under deps.dev:version directly', giving an explicit when-not-to-use and an alternative path. This is exemplary guidance.

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