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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, destructiveHint. The description adds valuable context: bundlephobia's first measurement can take 5-30s, sources_failed will list if it times out, and the rest still returns. 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 relatively long but well-structured and dense with information. It is front-loaded with the composite check concept and use case, then details return fields. Every sentence adds value, though it could be slightly trimmed without losing clarity.

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 tool has 2 parameters and no output schema, the description compensates by listing return fields, explaining error handling (partial failures), timing (5-30s), and ecosystem scope. It is complete enough for correct selection and invocation.

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 descriptions for both parameters. The description adds extra value by explaining that 'package' accepts scoped names like '@types/node' and that 'version' defaults to latest. This goes beyond the schema's basic descriptions.

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 it is a composite check for npm packages, scanning across deps.dev and bundlephobia, and specifies the use case: 'is X safe / popular / small' or 'what does adding lodash cost me'. It distinguishes itself from siblings by explicitly stating 'NPM ecosystem only in v1' and mentioning alternatives for other ecosystems.

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 explicitly says 'Use whenever an agent asks...' and provides clear scope (NPM only) with alternatives for other ecosystems (PyPI/Maven/Cargo/Go fall under deps.dev:version directly). It also notes partial failures and timing considerations.

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