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

Discloses partial failure behavior, bundlephobia's first measurement can take 5-30s and may result in sources_failed. Adds external service fan-out context beyond what annotations (readOnly/idempotent) provide, with no contradiction.

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 front-loaded with the core purpose, then logically covers usage, return fields, ecosystem limits, and failure handling. Each sentence serves a distinct function without redundancy.

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 no output schema, the description enumerates the summary block fields and other return elements. It also covers ecosystem scope and partial failure behavior, making it self-sufficient for 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 already documents both parameters at 100% coverage, so the description adds little. It reinforces the package is npm but does not introduce new parameter details beyond the schema.

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?

Clearly states it's a composite 'should I add this npm package' check in one call, fanning out to deps.dev and bundlephobia. Distinguishes itself with NPM-only scope and alternative tool 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?

Explicitly says use whenever an agent asks 'is X safe / popular / small' or 'what does adding lodash cost me'. Also specifies NPM ecosystem only and directs PyPI/Maven/Cargo/Go users to deps.dev:version directly.

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