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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the read-only nature is known. The description adds useful context by specifying that only paid expenses are included and defining the time periods (today and month-to-date). It does not mention return format or any aggregation behavior, but that is less critical with annotations present.

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, front-loaded sentence conveys the purpose without any wasted words. It is appropriately concise for a simple zero-parameter tool.

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 summary tool with no parameters and no output schema, the description is reasonably complete. It covers the subject (paid expenses) and time range (today and month), though it leaves ambiguous whether the response is one total or two separate figures. This is a minor 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?

The tool has zero parameters, and the schema is an empty object with 100% coverage. Per guidelines, the baseline for 0 params is 4, and the description does not need to add parameter details. It adds meaning by indicating the nature of the summary.

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 clearly states the tool reports how much the user has spent, specifically on paid expenses today and this month to date. It distinguishes from siblings like sales_summary and expense_accounts by mentioning 'paid expenses' and time ranges, though it lacks an explicit verb like 'get' or 'list'.

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 implies usage when the user wants a quick view of paid expenses for today and this month. It does not explicitly state when to use this tool versus alternatives such as search_expenses or expense_accounts, nor does it mention exclusions or prerequisites.

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