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

Adds real behavior beyond the annotations: $0.03/company pricing, "unresolved lookups never charged", per-field evidence with confidence scores, and honest nulls. These are exactly the cost/quality characteristics annotations cannot express. It doesn't restate the idempotent/openWorld hints, and there is no contradiction with readOnlyHint=false (a paid call is reasonably non-read-only).

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 enough that the core purpose lands early, but it opens with a sentence fragment ("Company name/domain/URL to a verified profile...") and repeats "per-field evidence + confidence" in two separate places, wasting one of its few sentences.

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 an output schema present, return values need no explanation, and the description supplies the sources, pricing, null/charge policy, and the country_hint trigger. The x402 payment flow is delegated to the x_payment schema field, which is acceptable but leaves the payment round-trip implicit in the prose.

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 the baseline is 3. The description restates that the input is a name/domain/URL and adds the reason for country_hint ('jp' for Japanese companies), but that value-add is marginal over the schema's own "ISO country hint for registry lookups, e.g. 'jp'". The x_payment mechanism is left entirely to the schema.

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 concrete transformation (company name/domain/URL into a verified profile) and names the actual primary sources (GLEIF LEI, Japan NTA corporate-number registries). This is far more specific than a generic 'look up company', though it never explicitly contrasts itself with the sibling jp_company_profile, leaving some ambiguity for an agent choosing between them.

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?

"Choose this when you have a company NAME or DOMAIN and need a registry-grounded profile" gives a clear triggering condition, and it tells the agent to pass country_hint 'jp' for Japanese companies. It lacks an explicit when-not or a named alternative (e.g. jp_company_profile), so it stops short of a 5.

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