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

Annotations already declare readOnlyHint, idempotentHint, and non-destructive nature. The description adds crucial behavioral details: it fans out to two services (deps.dev and bundlephobia), notes that bundlephobia's first measurement can take 5-30 seconds, and explains partial failures degrade gracefully with a sources_failed list. No contradiction 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 informative but somewhat lengthy. However, it is front-loaded with the core purpose and each sentence adds value. Minor improvement would be to shorten the list of return fields, but overall it maintains good structure.

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 complexity of the tool (composite check, two services, multiple return fields) and no output schema, the description is remarkably thorough. It lists all return fields in parentheses, explains failure behavior, and mentions version history and links. The agent can fully understand inputs, outputs, and edge cases.

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 described. The description adds value beyond the schema: it clarifies that scoped packages (e.g., '@types/node') are accepted for the 'package' parameter, and that 'version' defaults to the latest published version. This enhances semantic understanding.

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 as a composite check for npm packages covering license, advisories, version history, and bundle size. It specifies the exact use case ('should I add this npm package') and distinguishes from alternatives by noting ecosystem limitations and mentioning deps.dev:version for other package managers.

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 provides usage guidance: 'Use whenever an agent asks 'is X safe / popular / small' or 'what does adding lodash cost me'.' It also includes when not to use (other ecosystems) and directs to alternative tools, which is exemplary for an AI agent's decision-making.

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