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

With no annotations, the description carries the burden itself. It discloses an auth requirement (API key) and specifies the principal data returned. It doesn't explicitly state that the operation has no side effects or describe error cases, but 'Get' plus the field list provides a clear read-only behavior for this simple tool.

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 tight sentences with no filler. The main purpose and return fields are front-loaded, and the auth requirement is the only extra operational note, earning 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 simple, single-parameter, no-nested-object tool with no output schema, the description gives the purpose, required inputs, and the settlement fields the agent should expect. It does not cover edge cases like missing settlements or error behavior, but that is a minor gap here.

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% and the only parameter already has a clear description ('The transaction to look up settlement for'). The tool description adds no new parameter-level information, so the schema carries the weight; 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?

Description uses a specific verb and resource: 'Get settlement details for a transaction' and clarifies scope by naming the fields returned (captured, settled, refunded, status). This clearly distinguishes it from the quote_* siblings and other get_* tools on different resources.

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?

Usage context is implied: call it when you need settlement details for a transaction. It does not explicitly state when not to use it or name alternatives, though no settlement-specific sibling exists; the instruction 'Requires an API key' gives a prerequisite rather than selection guidance.

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