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

readOnlyHint=true already declares this as a safe read, so the description carries a lower burden. It adds the GET endpoint and the shape of the returned data, but says nothing about auth requirements, pagination, or scoping, which leaves minor gaps for a settings-listing tool.

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 compact sentences plus an endpoint reference; the returned fields are front-loaded before the usage hint. No filler, though the '(ciselne rady)' gloss is slightly decorative.

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?

There is no output schema, so describing the returned fields is genuinely necessary and done here. Combined with the readOnly annotation and the create_invoice link, an agent has enough to call and use this correctly, barring pagination details.

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 tool takes zero parameters, so there is nothing to document and the baseline is 4. The description correctly does not invent parameter semantics.

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 the resource (numbering series of the account) and enumerates the returned fields (id_number_series, document type, name, number pattern), so an agent knows exactly what this returns. It lacks an explicit verb but the title 'List number series' and the GET endpoint make the action 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?

It gives concrete downstream guidance: 'Use the id in vyfakturuj_create_invoice,' which tells the agent why and when to call this relative to a sibling. There is no explicit when-not or exclusion, but the workflow context is clear.

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