check_vat_registration

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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, covering the safety profile. The description adds useful behavioral context beyond that: it returns a vat_registered flag, the VAT ID, and a link to the ARES record, making the tool's behavior and output nature clear.

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 compact and well-structured: it front-loads the primary purpose, then clearly separates Args and Returns. Every sentence contributes useful information with no repetition or filler.

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?

Given the low complexity of the tool (one required parameter, a straightforward output schema, and safe annotations), the description is complete. It explains the input, the output fields, and the tool's core behavior without leaving significant gaps.

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?

The schema only defines 'ico' as a string with no description, so schema coverage is 0%. The description compensates by explaining that ico is the company's IČO, which gives essential semantic meaning. It could provide more format or validation details, but for a single identifier parameter this is a solid clarification.

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 states the tool's purpose: checking whether a company is an active VAT payer and returning its VAT ID. This distinguishes it from siblings like validate_ico_number (which likely validates IČO format) and lookup_company (which probably retrieves broader company data).

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 implies when to use this tool: when you need VAT registration status or a VAT ID for an IČO. However, it does not explicitly mention alternatives or state conditions under which another sibling tool would be more appropriate.

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