ares_validate_ico

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

With no annotations, the description carries the full burden. It discloses the pure, side-effect-free nature, the lack of ARES calls, and the return value (normalized IČO and validity). Minor edge cases like error behavior for malformed input are not described, but this is acceptable for a pure validation function.

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, front-loaded with the verb and resource, with zero filler or redundancy. Every clause contributes useful information.

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?

This is a low-complexity tool with one parameter fully covered by the schema. The description states the return fields explicitly, making it complete despite the lack of an output schema. Any missing error-behavior details are non-critical for typical usage.

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 schema description coverage is 100%, fully documenting the `ico` parameter with examples. The description adds no additional parameter semantics beyond referring to the normalized output, so baseline 3 is appropriate.

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 validates a Czech IČO using the ČSÚ Mod-11 checksum and identifies it as a pure function. It explicitly contrasts with the ARES lookup siblings by saying 'does not call ARES,' making its scope unique.

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?

'Pure function — does not call ARES' signals this is for quick local validation rather than authoritative ARES lookups, giving clear context. However, it does not explicitly name alternative tools or state when not to use it, so it stops short of a 5.

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