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

The annotations already signal this is not read-only (readOnlyHint=false) and not destructive (destructiveHint=false), so the 'Create' wording is consistent rather than additive. The description adds the multicurrency prerequisite and clarifies what a company currency represents, but it does not disclose behaviors like duplicate-currency errors, idempotency, or required permissions.

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 two short, direct sentences with no filler. The primary action is front-loaded, and the additional context about multicurrency and the resource meaning earns its place.

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 create-with-nested-object tool, the combination of description and rich schema covers the prerequisite, the object shape, and the sensitive-data restriction. It does not describe return values or error conditions, but no output schema exists and the create action is predictable enough that this is a minor gap.

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%, so the schema already documents the entity object, the company selector, and the ISO 4217 Code requirement. The main description adds little parameter-level detail, but that is acceptable because the schema carries the semantic load.

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 action ('Create a company currency') and a specific resource ('in QuickBooks Online'), which is unambiguous. It also distinguishes itself from sibling tools like update_company_currency, delete_company_currency, get_company_currency, and search_company_currencies by being the create operation.

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 gives clear context about when this is applicable: 'only meaningful with multicurrency enabled' and the schema reinforces the prerequisite. It does not explicitly name alternatives or exclusion cases, but the multicurrency precondition is a useful and clear usage signal.

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