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

Beyond annotations (readOnly, idempotent, openWorld, non-destructive), the description discloses performance characteristics (first bundlephobia measurement can take 5-30s), partial failure behavior (sources_failed will list it, rest still returns), and the default version behavior. This adds significant context without contradicting any 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 opens with purpose, then usage, then output summary, then ecosystem scope, then failure behavior. Structured logically with no redundancy or fluff, appropriately sized for 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?

For a composite tool with no output schema, the description thoroughly covers return values (summary block fields, per-advisory detail, links, alternative versions), ecosystem limitations, performance caveats, and graceful degradation. The only minor omission is explicit error handling for invalid package names, but the graceful failure note covers unlisted scenarios adequately.

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 coverage is 100%, so the baseline is 3. The description correctly references version defaults and accepted package names, but it does not add meaning beyond what the schema already provides. The description's mention of 'recent alternative versions' pertains to output, not parameter semantics.

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 opens with a specific verb and resource: 'Composite "should I add this npm package to my project" check in ONE call' and details the data sources (deps.dev, bundlephobia). It clearly distinguishes itself from sibling tools by being npm-package-specific and composite, not just a generic research or scan tool.

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 the tool: 'Use whenever an agent asks "is X safe / popular / small" or "what does adding lodash cost me"'. It also provides an exclusion and alternative: 'NPM ecosystem only in v1; PyPI / Maven / Cargo / Go fall under deps.dev:version directly', guiding the agent to alternative behavior for non-npm packages.

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