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

Annotations already declare destructiveHint=true, openWorldHint=true, idempotentHint=false and readOnlyHint=false, so the safety profile is largely supplied. The description adds real value beyond that: Paylyte holds no wallet, missing payment returns the 402 challenge with price and maxAmountRequired, and unknown paths are refused. However, it never addresses the non-idempotent risk (that a retry could charge twice) or whether payment is refundable, which is the most consequential behavior for a money-spending tool.

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?

Front-loaded with the action and price/rail, then the input contract, then the failure modes. Sentences are dense but each carries information; the side note about not writing or editing Core is the only borderline line.

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?

For a five-parameter, no-output-schema mutation tool, the description covers cost source, payment precondition, the 402 fallback, and rejection of unknown paths — enough to call it correctly. The main gap is what a successful response contains and retry/idempotency behavior, both of which matter for a paid call.

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%, so each of the five parameters is already documented in the schema. The description restates the two central inputs (path and X-PAYMENT) but adds no syntax, allowed values, or conditional rules beyond what the schema says, 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 a specific verb and resource (buys one live paid offering) plus the scope ('from the same catalogue shown on agent cards') and the payment rail (x402, priceUsd). An agent can tell this is the purchase step rather than discovery, but the description never names the sibling tools, so differentiation is inferred 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?

Clear context for invocation: the caller must already hold a signed X-PAYMENT for a specific path, and omitting payment yields a 402 challenge instead of an error. It does not explicitly tell the agent to call discover_live_offerings first or name any alternative, so it falls short of full when/when-not guidance.

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