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

Annotations already provide readOnlyHint, openWorldHint, idempotentHint, destructiveHint. The description adds valuable behavioral context: fans out to two external services, bundlephobia's first measurement can take 5-30s, partial failures degrade gracefully with sources_failed field, and the exact return structure. No contradictions.

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 one paragraph but efficiently packs all necessary information: purpose, when to use, external services, behavior, return format, and edge cases. No filler words; every sentence adds value.

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?

Given the moderate complexity (2 parameters, no output schema), the description is remarkably complete. It explains the composite nature, external dependencies, timing issues, fallback behavior, and the exact fields returned. It compensates for the lack of an output schema by enumerating the return structure.

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 clear descriptions for both parameters. The description adds value by clarifying that scoped packages (e.g., '@types/node') are accepted, which is not in the schema. Otherwise, the description does not introduce new semantic information beyond the schema, but the addition justifies a score above baseline 3.

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 is a composite check for evaluating npm packages, specifying the verb 'scan', the resource 'dependency', and the exact services used (deps.dev and bundlephobia). It differentiates from sibling tools by defining its specific scope (npm ecosystem, specific checks).

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 describes when to use ('whenever an agent asks 'is X safe / popular / small' or 'what does adding lodash cost me'') and when not to (NPM ecosystem only; other ecosystems fall under deps.dev directly). Also mentions partial failures and graceful degradation.

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