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

Annotations already declare readOnlyHint=true, so safety is covered. The description adds useful behavioral scope by specifying 'since it was opened' and 'by payment type', but it does not describe auth requirements, rate limits, or response shape beyond the basic result content.

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?

The description is two short sentences with the key scope and use case front-loaded. There is no filler, and the endpoint reference is compact.

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 read-only single-parameter tool with no output schema, the description supplies enough scope and result meaning (payment totals by payment type since opening) for an agent to call it correctly. Return format details are not provided, but they are not essential for invocation here.

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 description coverage is 100%, and the schema itself explains that register_id comes from list_registers. The description does not add parameter-specific syntax or meaning beyond what the schema already provides, so the baseline of 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 states a specific outcome (payment totals by payment type) and a clear scope (one register, since it was opened). It is easy to distinguish from list/register tools, though it does not explicitly name sibling alternatives such as sales_summary.

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 phrase 'end-of-day / cash-up view' gives a clear usage context for when an agent should select this tool. It does not state when not to use it or name a specific alternative, but the intended scenario is clear.

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