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

No annotations exist, so the description carries the full burden. 'Lookup' clearly indicates a non-mutating read, but nothing is disclosed about not-found behavior, rate limits, authentication needs, or response shape. This is adequate for a simple read operation but leaves notable gaps.

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 with no filler: the first lists the returned fields, the second specifies the input format. Everything earns its place and the key purpose 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 simple one-parameter lookup with no output schema, the description covers the essentials: what the tool returns and what input it accepts. It stops short of explaining error/not-found behavior or explicitly routing to sibling tools, but given the low complexity, it is largely complete.

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% (the id property already includes examples), so baseline is 3. The description adds value by explicitly stating the format constraints ('IČO (8 digits) or DIČ (CZ+10)'), which reinforces and clarifies the schema's examples beyond a mere restatement.

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?

States a specific verb ('lookup'), resource ('Czech company' in ARES), and the returned fields (name, legal form, address, NACE, data-box, VAT DIČ). This clearly distinguishes it from siblings like search_company (search by other criteria) and check_vat (VAT-specific) without needing to inspect schemas.

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?

Implies usage when you have an IČO or DIČ and need basic register data, but gives no explicit 'use this when' or 'not when' guidance. It does not mention alternatives such as check_vat or search_company, leaving the agent to infer which tool fits which scenario.

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