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

With no annotations, the description carries the full burden and it does disclose a genuinely important behavioral trait: the tool is paid ($0.010000 USDC via x402), which the agent must know before calling. It does not discuss failure modes (e.g., insufficient payment) or confirm the operation is a safe read, but the cost disclosure is substantive context beyond the schema.

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?

A single dense sentence with no wasted clauses; every element (cost, trigger, returned fields) earns its place. The cost is front-loaded before the purpose, which is slightly odd ordering, but the compactness is appropriate.

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?

No output schema exists, so the description must enumerate return values, which it does (version, summary, license, dependency count, downloads). The payment flow is covered by the schema's 'payment' parameter, leaving only error/edge behavior unstated for a low-complexity 3-parameter 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 description coverage is 100% and all three parameters (name, payment, ecosystem) are documented in the schema with defaults and formats. The description adds ecosystem coverage ('PyPI or npm') and output fields but no syntax or default details beyond what the schema already provides, so baseline 3 applies.

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 the resource ('package-registry metadata for one package (PyPI or npm)') and enumerates the returned fields (latest version, summary, license, dependency count, 30-day downloads). No competing sibling exists, so no explicit differentiation is needed, but the retrieval verb is only implied by the title rather than stated.

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?

'Call before adding or upgrading a dependency' gives a clear, actionable trigger condition for using the tool. There are no exclusions or named alternatives, but no sibling tool overlaps with package-registry lookup, so the guidance is sufficient context.

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