Get Available Rails

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

Annotations already cover the read-only/idempotent/non-destructive profile, and the description adds materially: the exact response shape `{ label, value, country }`, the fact that no API key is required (public endpoint), and a caveat that `country` is a display flag hint rather than a coverage guarantee. The last point preempts a very likely agent misinterpretation.

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?

Three sentences with no filler: identity of the resource first, downstream usage second, response shape and caveat last. The auth note is appended rather than buried, and nothing is repeated from the schema or annotations.

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 public list endpoint with no output schema, the description supplies the return shape, the field meanings, the auth requirement, and the consumption path. An agent has everything needed to call it and use the result 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?

There are zero input parameters, so the baseline is 4 by rule. The description instead spends its words documenting output field semantics (`value` vs `country`), which is useful but not strictly a parameter concern.

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 verb and resource ('Lists every payout rail BlindPay supports') and enumerates the actual values returned, so an agent knows exactly what comes back. It is clearly distinguishable from GetV1AvailableBankDetails, which it names as the downstream consumer.

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?

Explains where the returned `value` is consumed — as the `rail` query parameter of `GET /v1/available/bank-details` and as the `type` when creating a bank account — which effectively positions this as a prerequisite discovery call. It stops short of an explicit when-not or a stated alternative, so it lands just under a perfect score.

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