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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), but the description adds genuinely new behavioral boundaries: it never charges, never starts checkout, never counts revenue. Those negative guarantees are the critical thing an agent needs before touching anything commerce-related, and they are not derivable from the 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?

Three short sentences with zero filler: what it returns first, then the payment-safety boundary, then the call condition. Nothing repeats the name and nothing is padding.

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?

An output schema exists, so the return shape needn't be spelled out, and the description supplies everything else an agent needs: purpose, the explicit-payment boundary, and when to invoke. For a zero-parameter discovery tool this is complete.

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?

The tool takes zero parameters, so there is nothing for the description to disambiguate; the schema is empty and fully closed. Baseline 4 applies for a parameterless tool where semantics are a non-issue.

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 concrete verb and resource — it returns the separate commerce MCP endpoint plus its explicit-payment boundary — so an agent knows exactly what it gets back. The domain is plainly distinct from the audit/one-minute/akari siblings, so no sibling disambiguation is needed.

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?

Gives an explicit trigger: call it only when a user or agent asks for paid verification or purchasable artifacts. The word "only" also supplies the exclusion — do not call it for ordinary capability discovery — which is exactly the when/when-not guidance the rubric rewards.

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