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

With no annotations, the description fully discloses behavior: what it returns (preferred rail, fallback endpoints, ISO 20022 hint, compliance signal), the difference between anonymous and keyed calls, and the need for a free API key to unlock full endpoint sets. No contradictions or omissions.

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 informative yet efficient, with each sentence adding value. It is front-loaded with the core purpose. Slightly verbose due to additional API key details, but still well-structured and clear.

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?

Given no output schema, the description details the return types and includes behavior for anonymous vs. authenticated calls. It covers edge cases and prerequisites, making the tool fully understandable for correct invocation.

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?

Schema coverage is 100% with each parameter described. The description adds context by linking amount and currency to rail scoring and providing an example, but it does not significantly extend beyond the schema descriptions. Baseline 3 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 states the tool resolves a human-readable alias to payment endpoints and routing metadata. It includes a specific example and distinguishes its use before initiating payments, clearly differentiating it from siblings like get_payment_requirements.

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 explicitly says when to use this tool: before initiating any payment to a pay: address. It also provides context for anonymous vs. keyed calls and references the sibling get_payment_requirements as an alternative that does not require a key, guiding appropriate tool selection.

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