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

Annotations already mark the tool as read-only and open-world, and the description adds substantial behavioral context: x402 payment cost ($0.003), a score_confiance match score, live vs. local vs. enabled coverage states, and the Spanish hoja registral behavior. This goes well beyond the annotations and helps the agent predict results and side effects.

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 three dense sentences, front-loaded with the core purpose and followed by coverage, match confidence, Spanish follow-up, and payment. The opening clause slightly restates the title, but every subsequent clause carries useful information, so the length is justified.

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 output schema is present and the input schema covers all parameters, the description provides what an agent needs: payment mechanism, coverage caveats, match confidence, country-specific follow-up, and the optional x402/api_key flow. No critical invocation detail is missing.

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?

All four parameters are fully documented in the schema, so the baseline is 3. The description adds useful interpretive context for q and pays by naming the covered countries and explaining that Spanish matches expose a hoja registral key for downstream use, which enriches the parameter semantics 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 states a specific action — 'company lookup by name' — and a clear resource: 'official European company registers in one unified schema'. It lists covered countries and distinguishes itself from country-specific siblings like search_french_companies by emphasizing pan-European and GLEIF/LEI coverage.

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 makes the intended use clear: find companies across European registers by name, with optional country filtering and a follow-up to get_spanish_company_acts for Spanish results. It does not explicitly state when to prefer sibling search tools like search_french_companies or search_bodacc_announcements, so it stops short of full exclusion guidance.

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