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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so safety is covered. The description usefully scopes the tool as a computation-only path that skips document synthesis. It does not mention rounding/precision behavior, how missing tax_rate or discount_amount are treated, or whether the calculation is a pure function of the payload — real gaps for a calculator, but partly offset by annotation coverage.

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 that leads with the verb and enumerates outputs, closing with the differentiator. No filler or redundancy.

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?

An output schema exists, so return values need no explanation, and the input schema is fully described. For a read-only, single-parameter calculation tool the description is largely sufficient; only calculation edge-case behavior (rounding, missing fields) is left unaddressed.

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 100% and the nested document property already documents items, tax_rate, discount_amount, and amount_paid. The description restates the outputs rather than adding meaning to the input, so baseline 3 applies.

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 verb (calculate) and resource (document totals) and enumerates exactly what is computed: subtotal, tax, discounts, grand total, balance due. The clause 'without full PDF synthesis' separates it from generate_document and convert_document in the sibling set.

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 'without full PDF synthesis' implies when to prefer this over generate_document/preview_document, but the guidance is inferential rather than an explicit when-to-use statement. No prerequisites, no named alternative, no exclusions are stated outright.

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