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

Annotations already indicate readOnlyHint=false and destructiveHint=false, so the agent knows this is a mutation that is not read-only. The description adds no behavioral context beyond the act of creating, such as side effects on company books, irreversibility, permission requirements, or response behavior. It does not contradict the annotations, but it also does not disclose anything beyond them.

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 a single direct sentence with no filler or redundancy. Every word contributes to stating the action and target system, and the most important information is front-loaded. This is an appropriately concise definition.

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?

The schema carries substantial parameter context, covering the nested entity structure and company parameter. However, the tool operates on a complex object with no output schema, and the description offers no high-level context about return behavior or how purchase differs from related transaction types. It is minimally viable but would benefit from a brief note on what a purchase represents in QuickBooks.

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%, and the input schema already provides detailed meaning for both parameters, including the required fields, PII handling warning, and company selection behavior. The description itself adds no parameter-level information, so the baseline score of 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?

The description states a specific verb and resource: 'Create a purchase in QuickBooks Online.' This clearly identifies the operation and the target system, and the noun 'purchase' distinguishes it from sibling tools like create_bill, create_purchase_order, or create_vendor_credit. It lacks explicit sibling differentiation, but the core purpose is unambiguous.

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?

No guidance is given for when to use this tool versus alternatives such as create_bill, create_purchase_order, or create_payment. The description simply names the action without explaining its typical use case, prerequisites, or exclusions. An agent must infer which financial document is intended.

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