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

No annotations are provided, so the description carries the full burden — and it does disclose the key operational trait an agent needs: a per-call cost of 0.001 USDC via x402. It also implicitly signals a read-only lookup and notes that downloads are npm-only, though it is silent on error behavior for missing packages.

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?

Two compact sentences: the first enumerates what is returned, the second front-loads the intended use, with a short pricing note appended. Every clause carries information; nothing is padded.

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?

With no output schema, the description appropriately enumerates the returned fields, and the 402 payment handshake is detailed in the schema. It stops short of covering failure modes (unknown package, invalid registry value), which would round out a paid lookup tool.

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% and the payment flow is fully documented in the paymentProof description, so the baseline is 3. The description adds real value beyond the schema by clarifying that the registry parameter determines which ecosystem is queried and that weekly downloads are only returned for npm.

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?

States a specific verb+resource (metadata for an npm or PyPI package) and enumerates the exact fields returned (latest version, release date, license, repo, weekly downloads). No sibling tool overlaps with package registry lookups, so an agent can select it unambiguously.

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?

'Use to check a dependency before installing' gives a clear when-to-use context. There are no stated exclusions or alternatives, but none of the sibling tools compete for this job, so the guidance is sufficient without them.

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