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

The description goes far beyond the readOnlyHint annotation, explaining critical behavioral nuances: an open day is not in the ledger, stock/COGS only move at close, closed days post as one consolidated sale via saleId, creditSales post immediately as credit invoices, cash is rounded but QR is not, and large receipts are handled individually. This prevents serious misinterpretation of the returned figures.

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 long, but almost every sentence addresses a distinct misinterpretation risk or clarifies an important return value, which is justified given there is no output schema. It is front-loaded with the return summary before the caveats, though tighter phrasing could reduce its overall length.

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?

With no output schema, the description carries full responsibility for explaining return semantics, and it does so thoroughly: open/closed behavior, saleId, creditSales, rounding rules, consolidated vs individual receipts, and the not_available state for companies without the paid add-on. An agent has enough information to call and interpret this tool correctly.

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 only parameter is 'date', and the schema already covers 100% of its meaning with 'YYYY-MM-DD in Malaysia time. Omit for today.' The description repeats this but does not add meaningful parameter-level detail beyond what the schema provides.

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 defines the resource ('Counter till's day'), scope (one date, default today, Malaysia time), and the specific outputs returned (receipt count, voided count, cash/QR totals, open/closed status, receipt ranges, credit sales). It also distinguishes this tool from ledger-level sibling reports by explicitly stating that an open counter day has not posted to sales_summary, cash_position, income_statement, etc.

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 provides strong context for when this tool is relevant: use it to inspect till-level day figures before they reach the ledger, and it explains how those figures relate to sales_summary, cash_position, income_statement, open_invoices, and ar_aging. It does not explicitly state 'use this instead of X', but the ledger-vs-till distinction gives clear practical guidance.

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