clients_vies_lookup

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

No annotations are provided, so the description carries full responsibility. It states the tool validates and returns validity status plus company details, which covers the external service dependency (EU VIES). However, it doesn't disclose behavior details like rate limits, VIES unavailability, network failure handling, or whether failures throw vs return status. For a read-only validation lookup with no annotations, the description is adequate but not rich.

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?

Two sentences, tightly packed with high information density. First sentence states what the tool does and returns; second sentence states when to use it. No filler, no repetition of schema content. Every clause earns its place.

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?

The tool is a simple validation lookup with only 2 params and no output schema. The description covers purpose, use-case, and return value sufficiently. It could slightly benefit from mentioning the response format/fields structure, but given the simplicity and full schema coverage, the description is adequately complete for an agent to select and invoke this tool 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 coverage is 100% and both parameters have descriptive names/examples in the schema itself. The description adds meaningful context by explaining the validation is 'against the EU VIES system' and the purpose ('before applying reverse charge'), which frames how vatCode is used. The companyId parameter meaning (company UUID override) is fully covered by schema; the description adds the reverse-charge business context beyond 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?

The description uses a specific verb ('Validate') with a clear resource ('VAT code against EU VIES system') and explicitly states output (validity + registered company name/address). It clearly distinguishes from siblings like anaf_validate_cif and clients_anaf_lookup, which target a different validation domain (Romanian ANAF vs EU VIES).

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 explicitly states when to use it ('to verify EU intra-community VAT numbers before applying reverse charge'), which provides clear use-case context. However, it doesn't explicitly exclude alternatives or mention when NOT to use it versus anaf_validate_cif or clients_anaf_lookup, leaving the boundary with those siblings implicit.

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