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

Beyond the readOnlyHint annotation, the description discloses important behavioral traits: the registers are refreshed daily, the tool returns authorisation dates, licensed PSD2 services, EEA passporting and withdrawals, and the absence of a licence is a meaningful answer. It also warns about the x402 payment cost, which is critical invocation context.

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 dense but every sentence earns its place: it front-loads the resource and scope, then gives usage guidance, clarifies empty-result semantics, and states the payment cost. No redundant filler or tautology.

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 a rich output schema and 100% parameter schema coverage, the description only needs to explain when and why to use the tool, what data it covers, and what the call costs. It does all of that, including payment behavior and data freshness, so an agent can select and 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 description coverage is 100%, so the parameters are already fully documented. The description adds no parameter-level detail beyond restating that the lookup is by SIREN and mentioning the payment method, which is already detailed in the schema for api_key and x_payment. Baseline 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 clearly identifies a specific resource: regulatory authorisations of a French company by SIREN. It enumerates the covered authorisation categories and source registers (EBA PSD2, EIOPA, ARCEP), which distinguishes it from siblings like get_french_company_profile or search_eu_financial_authorisations.

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 gives explicit usage context: "Use it before paying, onboarding or contracting with a regulated counterparty." It also says "Not authorised is an answer too," guiding the agent not to treat an absent authorisation as an error. However, it does not name alternatives or exclusion conditions, so it falls 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.