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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so the safety profile is covered. The description adds the key behavioral nuance beyond that: the data mirrors the payout settings page config rather than a live provider check, which tells the agent results may be static. Freshness/refresh policy is still unstated, keeping it below 5.

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, front-loaded with the core answer (countries + rail), followed only by useful exclusions. Nothing is repeated from the title and no sentence is filler.

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?

With no output schema, the description must convey the return shape, and it does minimally: a set of countries plus an associated rail value. It stops short of describing the exact field names or shape of each entry, which would fully close the gap for a zero-param, no-output-schema lookup.

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 takes zero parameters, so there is nothing for the description to disambiguate; the schema is trivially complete. Baseline of 4 applies with no semantic gaps.

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 resource (payout countries) and the associated payload (rail: Stripe or Wise), which an agent can distinguish from get_supported_currencies or get_payout_methods. It never uses an explicit verb like 'list' or 'return', so the action is inferred from the noun phrase 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?

The two negative clauses ('does not check a live provider', 'does not return bank details') implicitly steer the agent away from using this for live provider verification or bank details. However, no sibling tool is named and no positive trigger for when to call this versus get_payout_methods is given, so routing is left to inference.

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