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

With no annotations, the description carries the burden of behavioral disclosure. It usefully adds that the operation is purely local and network-free and exposes the checksum algorithms (mod-11, mod-97). However, it does not describe the output shape, whether any input is required, or how failures are represented.

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 tightly packed sentences: the first names the operation and enumerates the covered formats with parenthetical algorithms; the second adds the key offline constraint. There is no filler, and the essential information is front-loaded.

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 has no annotations and no output schema, so the description alone must explain what callers get back. It covers inputs and offline behavior, but omits return value semantics, whether at least one parameter is required, and how invalid input is reported. These are important gaps for a validation tool.

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 description coverage is 0%, so the description is the only semantic source for params. It meaningfully maps each schema field to a concrete identifier type and validation rule: dic as DIČ, ico as IČO mod-11, iban as IBAN mod-97, variableSymbol as variable symbol. It does not detail variable symbol criteria, but the description adds substantial meaning beyond the raw string properties.

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 clear verb scope: 'Checksum/format validation' of specific Czech identifiers (IČO, DIČ, IBAN, variable symbol). It is focused on a recognizable resource, though it does not explicitly differentiate itself from check_vat or company_lookup.

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 gives no context for when to choose this tool over siblings like check_vat, which likely covers similar VAT-related identifier checks. The only usage hint is 'Pure local, no network,' which implies offline suitability but does not state exclusions or alternatives.

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