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

Beyond the readOnlyHint and openWorldHint annotations, the description discloses critical behaviors: open vs closed status affects whether anything has posted, credit sales post immediately as ordinary credit invoices, cash and QR totals exclude credit sales, QR is never rounded, and the tool returns not_available without the paid add-on. These are exactly the behavioral details an agent needs and there is no contradiction with the annotations.

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 front-loaded with the core purpose and return fields, and the extensive accounting details are justified because there is no output schema. However, it is a dense single paragraph with formula-heavy asides, which makes it harder to scan than a more structured presentation would be.

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?

Given the lack of an output schema, the description is thorough: it explains all major return fields, the open/closed accounting implications, credit-sales treatment, drawer reconciliation math, e-invoice thresholds, and the paid add-on case. An agent has enough context to interpret the result 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?

Schema description coverage is 100% for the single optional `date` parameter, already documenting the YYYY-MM-DD format, Malaysia time, and default of today. The description repeats the default and Malaysia-time framing but adds no meaningful syntax or semantics beyond the schema, so the baseline 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 resource, the Counter (Kaunter) till's day for one date, and enumerates what it returns: receipt counts, cash/QR totals, rounding, status, receipt range, and credit sales. It also distinguishes this from sales_summary, cash_position, and income_statement by explaining ledger timing, so an agent can identify it without ambiguity.

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 clear context for when the figures are meaningful, especially the open-vs-closed distinction and the warning that open-day till figures are not in sales_summary, cash_position, or income_statement. It names relevant alternatives indirectly, but does not give a crisp "use this instead of X when Y" routing statement, so it falls short of full explicit alternatives guidance.

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