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

Annotations cover read-only/idempotent/open-world safety, and the description goes well beyond them by disclosing the paid access model: x402 USDC on Base, $0.002 per successful call, and the fact that an unpaid call returns a PaymentRequired object. That payment/auth behavior is not derivable from any structured field and is exactly the kind of context an agent needs.

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?

Three sentences, front-loaded with the 'Use when' trigger, then the version convention, then the payment caveat. The field enumeration is a bit long but each item is a real return attribute and no sentence is redundant filler.

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?

There is no output schema, so the description's enumeration of returned file fields carries the return-value burden and does so concretely. Combined with the payment disclosure and the required-parameter guidance, an agent has everything needed to call this correctly.

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 both parameters are documented there, so the baseline is 3. The description restates the 'latest' convenience value already present in the schema and adds no syntax, format, or constraint details beyond it.

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: retrieving published artifacts (files) for a specific PyPI version, with an explicit enumeration of what each file carries (filename, packagetype, size, digests, URL). The scope 'for a specific PyPI version' implicitly separates it from pypi_project and pypi_search, but no sibling is named outright.

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 when you need the published artifacts for a specific PyPI version" gives a clear triggering condition, and the 'latest' shortcut tells the agent how to handle the common case. No explicit when-not or named alternative (e.g., pypi_project for project-level metadata) is provided.

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