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

Annotations already cover safety (readOnly, idempotent, openWorld), so the description's real contribution is the payment handshake: $0.25 per call via USDC on Base x402, and that it returns payment requirements unless payment_signature is supplied. That is behavior an agent cannot infer from annotations or schema, and it also points to a sample. It says nothing about result contents or failure modes, but the paid-call flow is well disclosed.

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 opening and "Use when onboarding or paying a new supplier" restate the same idea, so one full sentence is largely redundant. It is nevertheless short and front-loads the purpose and the routing cue before the pricing details.

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, the description should indicate what the compliance check returns (e.g. registry match, sanctions hits, export-control flags). It instead leaves the response shape entirely to the x402 payment requirements note, which is a meaningful gap for a compliance-aggregation tool.

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% and every parameter has a self-explanatory description (LEI, VAT, EORI, name, country, payment_signature), so the baseline is 3. The description adds no parameter-level detail such as which identifier is most authoritative when several are supplied.

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 ("Check a new supplier") and the scope of checks in the title (VAT, EORI, Company, Sanctions, Export Control). The "in one call" phrasing distinguishes it as an aggregate check versus the single-purpose siblings like check_vat or check_eori, though it never explicitly names the very similar counterparty_due_diligence.

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 when onboarding or paying a new supplier" gives a clear triggering context. It stops short of exclusions or naming alternatives, so an agent choosing between this and counterparty_due_diligence or batch_sanctions_screen gets no routing rule.

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