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

Annotations already cover safety (readOnlyHint=true, destructiveHint=false), and the description adds worthwhile behavioral context: it queries the external ARES registry and returns a structured customer-shaped object. It does not disclose failure modes or rate limits, but for a read-only lookup this is a minor gap given the annotation coverage.

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?

A single sentence packs purpose, data source, returned fields, use case, and output shape into a compact definition. No filler or repetition; the most important 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?

For a one-parameter read-only lookup with no output schema, the description is complete: it explains the source, the data returned, the output shape reference, and the intended business scenario. An agent has enough to call the tool correctly and map the result forward into an order.

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 coverage is 100% and the schema already documents ico as 'IČO (7–8 číslic)'. The description repeats the IČO concept but adds little beyond schema semantics; it does confirm the parameter identifies the company to look up in ARES. Baseline 3 is appropriate because the schema carries the parameter-meaning burden.

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 ('Dohledá firmu podle IČO v ARES'), identifies the exact resource (ARES registry), and lists the data returned (název, DIČ, sídlo). It also ties the result to a concrete use case ('pro nákup na firmu') and connects the output shape to create_order.customer, making it easy for an agent to distinguish this lookup tool from order-management siblings.

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 clearly indicates when this tool is relevant: when purchasing as a company and you need Czech company details by IČO. It does not explicitly name sibling alternatives or state when not to use it, but the ARES-specific lookup intent and the create_order.customer output shape provide enough contextual guidance.

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