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

Annotations already declare readOnly/idempotent/non-destructive/openWorld, and the description adds materially more: it is free, rate-limited to 100 lookups per day per IP, and it spells out conditional return semantics (VAT id only for VAT payers, county as ISO code, Bucharest as SECTOR1..6, plus inactive/VAT-on-collection/e-Factura flags). That is exactly the context an agent needs before committing to a call.

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?

It is front-loaded with 'Use when...' and every clause carries information, though the returned-field enumeration is dense and could be split for readability. No filler sentences.

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 carries the burden of explaining returns and does so field by field, including conditional quirks like RO-prefix and sector encoding. An agent can call it and interpret the result without further documentation.

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 single parameter has 100% schema coverage and the schema already says 'CUI, with or without RO'. The description only reinforces that it is a Romanian CUI, adding no format or edge-case detail beyond the schema, so the baseline of 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?

The description names a specific verb and resource (lookup a Romanian company by CUI) and states the exact data returned (ANAF legal name, VAT id, trade register, address, flags). It is immediately distinguishable from the invoice-generation and validation siblings in the same namespace.

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?

It gives two concrete trigger scenarios: building/checking an invoice when only the CUI is known, and vetting a partner before invoicing. There is no explicit exclusion or named alternative, but the context for use is unambiguous.

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