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

Beyond the annotations (readOnly, idempotent, non-destructive), the description discloses important operational behavior: partial failures degrade gracefully, bundlephobia's first measurement can take 5-30s, and sources_failed will list timeouts while the rest still returns. It also lists the output summary block fields, giving the agent a clear picture of what to expect. This is rich behavioral context that goes beyond the structured metadata.

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 about 120 words and heavily packed with useful information, but it's not overly verbose. It is front-loaded with the core purpose, then flows into usage guidance, output shape, exclusions, and failure behavior. A slight deduction because the list of return fields is long and could be summarized, but overall every sentence earns its place.

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 the return value (summary block fields, per-advisory detail, links, recent alternatives), ecosystem scope, and timing/failure behavior. It leaves no critical gaps for an agent to know what the tool does and how to interpret its results. This is complete in context.

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 doesn't add much parameter-specific meaning beyond the schema's own descriptions; it restates that 'package' is an npm package name and mentions scoped packages are allowed (already in schema). The 'version' default behavior is also in the schema. Therefore the description adds value in context (e.g., 'NPM ecosystem only') rather than in parameter semantics, so a 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 opens with a specific and informative definition: 'Composite "should I add this npm package to my project" check in ONE call' and details the two data sources (deps.dev and bundlephobia) and the exact facets evaluated (license, advisories, bundle size, etc.). This clearly identifies the tool's function and distinguishes it from sibling tools like bet_research or deep_research, which have different domains.

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 provides explicit when-to-use guidance: 'Use whenever an agent asks "is X safe / popular / small" or "what does adding lodash cost me"'. It also gives an exclusion: 'NPM ecosystem only in v1; PyPI / Maven / Cargo / Go fall under deps.dev:version directly' — a helpful pointer to alternatives without naming a sibling. This is exemplary usage guidance.

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