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

Annotations already declare readOnly, idempotent, non-destructive, but the description goes beyond by disclosing graceful degradation on partial failures, the 5-30s first-measurement timeout for bundlephobia, and the sources_failed field. It also notes NPM-only v1 scope. No contradictions with 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 five dense, information-rich sentences, each earning its place: purpose, usage, output fields, ecosystem scope, and failure behavior. It is front-loaded with the main check and avoids redundant repetition of the title or schema.

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 multiple data sources, the description fully accounts for complexity: it lists output fields, mentions per-advisory detail and links, specifies ecosystem limits, and explains timeout/partial-failure behavior. With no output schema, the description itself supplies the necessary return-value 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 baseline is 3. Both parameters have clear descriptions in the schema (package name with scoped support, version defaulting to latest). The description adds no new parametric meaning beyond what the schema already provides, though it does contextualize the parameters within the composite check.

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+resource: 'Composite "should I add this npm package to my project" check in ONE call' and explicitly names the two fan-out sources (deps.dev and bundlephobia). It clearly distinguishes this tool from siblings (none of which are npm package analysis) and states the ecosystem limitation.

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?

Explicit usage triggers are given: 'Use whenever an agent asks "is X safe / popular / small" or "what does adding lodash cost me"'. It also provides a when-not: 'PyPI / Maven / Cargo / Go fall under deps.dev:version directly', directing users to alternative handling for other ecosystems.

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