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

Beyond the annotations (readOnlyHint=true, openWorldHint=true), the description discloses the paid-call model, price ($0.12 USDC), the x402 payment mechanism and chains, auto-pay clients, and a caveat that a sanctions match requires manual verification. That is significant behavioral context an agent cannot get from structured fields.

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-loaded with the core capability and outputs before prerequisites, pricing, and the sample call. The dense multi-topic run-on sentences are efficient but slightly packing-heavy, keeping it just below maximum.

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 fully compensates by describing return shape (grade, score, verdict, reasons, confidence, sections). It also covers cost, payment, prerequisites, caveats, and provides a concrete example input, leaving nothing an agent needs to invoke it correctly.

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 requires no fields, but the description supplies the actual invocation rule: 'Pass name and at least one of vat_number, lei, domain.' That corrects the empty required list and adds meaning beyond the 67%-covered schema. It could add format details for country/domain, hence a 4 rather than 5.

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 names a specific verb and resource ('Full EU company check') and enumerates the concrete checks bundled (LEI status, VIES VAT, sanctions, domain age, email security, IBAN). It returns specific outputs (grade A-F, score 0-100, ALLOW/CAUTION/BLOCK), so an agent can distinguish it from siblings like company_lookup, vat_validate, or sanctions_screen.

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?

It states the usage context ('Use for onboarding and payment checks') and explicitly frames the sanctions result as a hint to verify manually, which is real usage guidance. It doesn't name sibling tools as alternatives, so it stops short of explicit when-not/alternative routing.

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