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

With no annotations, the description carries the burden of behavioral disclosure. It clearly states the tool returns masked sources and includes a guardrail ('Never request secrets'), which is valuable. The read-only nature is implied by 'List,' and the warning about secrets further clarifies expected behavior, though it does not detail error handling or response structure.

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 two short sentences with no filler. The first sentence states the core function and the second adds a critical safety rule. Every word earns its place, and the most important information is front-loaded.

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 list tool with no output schema, the description is complete: it tells what is returned (masked payment sources, unattended-settlement flag) and the key constraint (never request secrets). An agent can select and invoke this tool correctly with the information provided.

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, and the schema is empty with 100% coverage. The description correctly adds no parameter-specific details because there are none. According to the rubric, a no-parameter tool gets a baseline of 4, and the description doesn't introduce confusion.

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 resource ('payment sources'), and clarifies the scope ('available to this agent'). It includes the key qualifier 'masked' and the capability indication ('whether each can settle unattended'), making it clearly distinct from siblings like list_payments or get_payment.

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 implies the use case: when an agent needs to see available payment sources without requesting sensitive details. It does not explicitly name alternatives or exclusion conditions, but the sibling tool names and the 'masked' phrase provide clear context. It would benefit from an explicit reference to a sibling for differentiation.

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