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

The description adds operational detail beyond the annotations by disclosing 'one voucher, one settlement, one signed XDR-1 receipt' and flat pricing. This is useful context for an agent deciding whether to invoke the tool. There is no contradiction with the readOnlyHint, since payment/settlement is not described as mutating external data in the validation sense.

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 dense sentences with no filler: the first presents the action, scope, and batching model; the second gives the pricing rationale. Key information is front-loaded and every clause 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?

Given the simple single-parameter schema, the existing output schema, and annotations, the description fully covers batching capability, payment behavior, and the economic reason to use it. An agent has enough to select and invoke the tool correctly without missing critical context.

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 input schema already provides 100% coverage for the single `items` parameter, including the `tool` enum and `value` descriptions. The description only restates the 'up to 50' limit and lists identifier types, adding no meaning beyond the schema, so the baseline of 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 opens with a specific action and resource: 'Run up to 50 identifier checks... in ONE paid call.' It also differentiates itself from the many individual sibling validator tools by emphasizing batching and the per-check cost advantage over single calls.

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 clearly signals batch use cases through 'up to 50 checks in ONE paid call' and '10x cheaper per check than single calls,' which implies choosing this over individual sibling tools for multi-item validation. It stops short of an explicit 'use individual tools for a single check' exclusion, but the context is clear enough.

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