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

Annotations already indicate read-only, idempotent, non-destructive behavior. The description adds significant context: composite fan-out to two sources, partial failure handling (sources_failed list), and a specific timing caveat (bundlephobia's first measurement can take 5-30s). This exceeds what annotations provide.

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 a single dense paragraph but well-organized: starts with core purpose, expands on what it fans out, then gives usage examples and limitations. It front-loads the most important information. Slightly verbose but maintains clarity. Minor redundancy (e.g., mentioning both 'npm package' and 'NPM ecosystem').

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?

Despite lacking an output schema, the description enumerates the return fields (summary block with is_latest, license, etc., per-advisory detail, links, alternative versions). It covers error handling (partial failures, sources_failed) and timing behavior. For a composite tool, this is thorough and leaves no major gaps.

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% with both parameters (package, version) already documented in the schema. The description does not add new meaning beyond what the schema provides, e.g., 'Scoped packages accepted' is already in `description` of `package`. Baseline 3 applies here.

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 evaluating an npm package before adding it to a project. It names the resources (deps.dev, bundlephobia) and distinguishes itself from any sibling tools by specifying the npm ecosystem scope. The verb 'scan' plus 'dependency' is specific and accurate.

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?

Explicitly instructs when to use: 'whenever an agent asks "is X safe / popular / small" or "what does adding lodash cost me"'. Also provides exclusion guidance: 'NPM ecosystem only in v1; PyPI/Maven/Cargo/Go fall under deps.dev:version directly'. Warns about partial failures and timing, offering clear context for invocation.

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