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

The '(read only)' note merely restates the readOnlyHint=true annotation, so it earns no credit beyond structured data. The description does add value by naming the returned fields (currency, number of entries, current balance), which matters because no output schema exists, but it omits any behavior on invalid/missing ids or error conditions.

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 fragments that lead with what is returned and the HTTP route; nothing is padded. Minor redundancy in the parenthetical '(read only)', which duplicates the annotation, keeps it from a 5.

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 single-parameter read tool with no output schema, the description covers the operation, the identifying parameter's source, and the shape of the returned data. Only error/not-found behavior is unaddressed, which is a small gap given the tool's simplicity.

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 single parameter already documents its type, positivity constraint, and provenance ('from superfaktura_list_cash_registers'). The description adds no format or syntax detail beyond the schema, so the baseline 3 applies.

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 (get) and resource (one cash register) plus the payload fields returned (currency, entry count, balance), so the agent knows exactly what it retrieves. The word 'One' implicitly contrasts with the sibling superfaktura_list_cash_registers, but that sibling is never named, so differentiation is left to inference.

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?

Usage is only implied: the schema note that the id comes 'from superfaktura_list_cash_registers' sketches a list-then-view workflow, and 'One ... register' hints at single-record retrieval. There is no explicit when-to-use/when-not statement and no named alternative, so an agent must infer the routing.

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