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

With no annotations, the description carries the full burden. It usefully discloses the billing cost ('Costs 1 credit') and hedges that headcount is returned 'when available', which tells the agent some fields may be null. It says nothing about auth requirements, rate limits, or whether the call is idempotent/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 with the return payload, then the input contract, then cost — a sensible priority order in three tight sentences. Slightly dense in the first sentence, 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, the description does the necessary work by enumerating the returned fields (officers with name/role, legal form, activity, address, headcount range). Missing only edge-case behavior such as what happens when the registration number is not found.

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 the schema already documents the country enum (FR = SIRENE/RNE, GB = Companies House) and the registration number format. The description restates 'SIREN for FR, company number for GB' without adding new constraints, so the baseline 3 applies.

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 clear verb+resource: returns extended registry data (officers, legal form, activity, address, headcount) for one company by registration number. Strong on scope, but it never distinguishes itself from the sibling verify_company, which plausibly covers overlapping registry territory.

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?

Usage is implied by the phrase 'extended registry data' and the 1-credit cost signal, which hints this is the heavier/paid option versus a plain verification call. However, it never states when to prefer this over verify_company or verify_vat, nor any prerequisites for the lookup.

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