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

Annotations only declare readOnlyHint/openWorldHint; the description adds substantial behavioral detail beyond them — default date and timezone, exclusion of accounts with no postings (and their count in accountsWithNoPostings), the hard rule that entries after asOf are never included, no year-end closing journal, and the sen-level balancing guarantee. It also explains contra-account placement so the debit/credit columns are interpretable.

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?

Front-loaded with purpose and default, then row shape, then totals, then exclusions, then the balance_sheet contrast — a sensible ordering. It is dense and the contra-account parenthetical plus the closing year-end note are long, though both earn their place by preventing misreading of the numbers.

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?

There is no output schema, and the description compensates fully by enumerating every row field (code, name, type, debit/credit, balance) with its sign convention, plus totals, balanced, and accountsWithNoPostings. An agent can both call this tool and interpret its response without further documentation.

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 0%, so the description must carry the parameter, and it does: asOf is described as a date with a default of today in Malaysia time, which the bare pattern in the schema does not convey. The exact date format is only implied by the schema pattern, not restated, keeping this just short of a 5.

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 resource (trial balance) with an explicit scope (as of a date, default today, Malaysia time) and anchors it to a concrete UI equivalent (Reports → Trial Balance). It is immediately distinguishable from balance_sheet, general_ledger, and income_statement, which are named directly.

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?

Explicitly contrasts behavior with two siblings: it says balance_sheet closes the year arithmetically while this tool does not, and that each balance equals general_ledger's closing for that account. It stops short of a prescriptive 'use this tool when X, use that when Y' routing sentence, so an agent still has to infer the choice rather than being told it.

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