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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false. The description adds useful non-obvious context by explicitly stating it does not buy a pass or authorize spending, which helps prevent misuse. No contradictory behavior is disclosed.

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?

Two short sentences deliver the purpose and the key limitation with no filler. The primary action is front-loaded, and every clause earns its place.

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 zero-parameter, read-only list operation, the description covers the action, the resource, and the important non-goal. No output schema exists, but the simple 'list' semantics make the return shape reasonably inferable and no additional calling context is needed.

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 has zero parameters, so the description cannot add parameter meaning beyond the empty input schema. Per the baseline for parameterless tools, this is sufficient; the description accurately reflects that no inputs are needed.

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 names a specific verb ('List') and a concrete resource ('supported payment currencies and networks'). It also clarifies what the tool is not for ('Does not buy a pass or authorize spending'), distinguishing it from purchase actions even though no sibling payment tool exists.

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 clearly frames when to use the tool: to enumerate supported payment currencies and networks. It adds an explicit exclusion for buying a pass or authorizing spending, but it does not name an alternative tool for those actions, so it falls just 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.