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

The description adds context about the data sources and identifier types per country (e.g., VIES, Bolagsverket), which goes beyond the readOnlyHint. It also explicitly limits the scope to non-Czech companies. There is no contradiction with annotations.

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 a single punchy sentence followed by a compact list. It front-loads the core purpose and then efficiently enumerates supported countries without redundant words.

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?

For a two-parameter lookup tool, the description is comprehensive: it covers all supported countries, identifier types, and sources. Annotations handle read-only and open-world semantics, so the description does not need to detail return values or error handling.

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 input schema already describes both parameters with examples, so the baseline is 3. The description enhances this by mapping each supported country to its expected identifier format (e.g., gb -> CRN, pl -> KRS), which is critical for constructing valid 'id' values.

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 function: retrieving a non-Czech company using an ID and country code. It distinguishes itself from sibling tools by listing the specific country-ID mappings, making the exact scope and method unambiguous.

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 provides clear context on when to use the tool (when you have a national ID and country code for a non-Czech company) and enumerates supported countries and identifier formats. It does not explicitly name alternatives or exclusions, but the high specificity implies the appropriate use case.

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