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

Annotations already declare readOnlyHint=true and destructiveHint=false, covering the basic safety profile. The description adds a meaningful behavioral guarantee: 'Never returns or accepts private keys,' which is useful context beyond the annotations and reassures agents about secret handling during invocation.

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 primary action is front-loaded, and the second sentence provides a concise, valuable safety qualifier. Every word 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, annotated read-only tool, the description is sufficient to understand what the tool does and what safety guarantees apply. No output schema exists, but 'List' adequately implies a collection return. The low complexity means the description is complete enough for an agent to invoke it correctly.

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 parameter semantics are trivially satisfied. Schema description coverage is 100%, and the description's note that it never accepts private keys usefully reinforces that no secret inputs are expected. The baseline of 4 for zero-parameter tools is appropriate.

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 uses a specific verb and resource ('List headless payout rails') and clearly identifies a read-only listing action. It does not, however, differentiate this tool from similarly named siblings such as get_payout_options or list_payment_methods, and 'headless' is jargon that is not explained.

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?

There is no guidance about when to use this tool versus alternatives like get_payout_options, list_payment_methods, or set_payout_method. The description does not state any preferred context, exclusions, or conditions that would help an agent choose among the closely related payout tools.

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