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

No annotations exist, so the description carries the full burden and it does volunteer one genuinely useful trait: the call 'Costs 1 credit'. It says nothing about authentication, failure modes for an unknown registration number, or result freshness/caching, which matters for a paid registry lookup.

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-loads the return payload, then the two required inputs, then the cost in one short clause. Every sentence carries information and nothing is repeated from the title.

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 correctly enumerates the returned fields and flags the optional headcount, so an agent knows what to expect. It is complete enough for a two-parameter read tool, with the only gap being error behavior on non-matching registration numbers.

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 both parameters are documented in the schema, including the FR/GB enum values and the SIREN vs company-number distinction. The description restates these mappings without adding format, validation, or lookup hints beyond the schema, so 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 specific verb and resource ('Returns extended registry data for one company') and enumerates the payload (officers/directors in office, legal form, activity, address, headcount range). It never names or contrasts with the sibling verify_company, so an agent must infer why it would use this enrichment call rather than the plain verification one.

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 input contract ('country (FR or GB) and the exact registration number'), which tells the agent the prerequisite keys but not when this tool beats verify_company or screen_sanctions. No when-not-to-use or alternative routing is given.

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