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

Annotations already declare readOnlyHint/idempotentHint/openWorldHint, so the safety profile is covered. The description adds real value beyond that: the $0.02 x402 price and the fact that it returns payment requirements instead of data unless payment_signature is supplied — a non-obvious two-path behavior worth disclosing.

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?

Front-loads the core purpose before pricing and payment flow, and each sentence carries distinct information (purpose, use cases, cost, payment semantics, sample). Slightly dense with commercial/plumbing detail but nothing is wasted.

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 and all four params documented, the description still conveys purpose, the payment-gated response path, and a sample pointer. An agent has enough to call it correctly; only an explicit alternative-tool routing hint is missing.

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 description coverage is 100%, so all four parameters (lei, name, children_limit, payment_signature) are already documented in the schema. The description only echoes the payment_signature gating behavior and adds no syntax or format detail, making the baseline 3 correct.

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+resource ('find out who owns or controls a company') and enumerates the outputs (parent chain, ultimate parent, subsidiaries). Clear, but it never names a sibling such as lookup_company or counterparty_due_diligence to disambiguate the ownership-focused scope.

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?

'Use for KYB, credit or group-exposure checks' gives concrete usage context an agent can match against an intent. It stops short of naming alternatives or stating when NOT to use it, so it stays at 4 rather than 5.

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