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

Annotations already indicate readOnlyHint=true and destructiveHint=false, so the description appropriately avoids repeating those. It adds valuable behavioral context by noting that the tool 'explicitly reports the receiver-only wallet boundary,' which is not covered by annotations and helps the agent anticipate the tool's output focus.

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?

The description is a single, focused sentence that leads with 'FREE' and immediately conveys the core action and unique output feature. Every word earns its place, with no filler or repetition.

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 simple read-only listing tool with no input, the description covers the primary purpose and a key output characteristic. It does not detail the exact return format or further explain what the receiver-only wallet boundary means, but that level of detail is not necessary for correct invocation. The provided info is sufficient for an agent to decide to call it.

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?

This tool has zero parameters, so there is nothing for the description to explain about inputs. The schema is trivially complete, and the description does not need to add parameter details. A baseline of 4 is appropriate for a no-parameter tool.

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?

The description clearly states the tool's action ('Lists') and the resource ('supported payment methods'), and adds a distinctive detail ('explicitly reports the receiver-only wallet boundary') that sets it apart from sibling tools. It is specific and unambiguous.

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?

The description does not provide any guidance on when to use this tool vs. alternatives, nor does it mention any exclusions or prerequisites. With many sibling tools, the agent is left to infer the appropriate selection context.

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