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

The annotations already flag the operation as destructive and non-read-only, and the description adds the important precondition that a current SyncToken is required to update. The richer behavior—sparse updates, Line replacement, sensitive-field restrictions—lives in the schema rather than the description, but the description still surfaces the key versioning/precondition trait beyond 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?

A single front-loaded sentence states the action, object, context, and the key precondition with no filler. Every word 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?

The schema fully documents sparse/full update semantics, line replacement, sensitive-field prohibitions, and company selection, while annotations cover the destructive nature. For this complexity level, an agent has everything needed to invoke the tool correctly, even without an output schema.

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 entity schema already explains the required Id/SyncToken, sparse vs. full updates, Line-array replacement, restricted fields, and the optional company parameter. The tool description repeats only the Id/SyncToken requirement, adding no new parameter meaning beyond what the schema already provides, so it sits at the baseline.

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 ('Update'), a specific resource ('an existing payment'), and the target system ('QuickBooks Online'). The words 'existing' and 'requires Id and SyncToken' clearly distinguish this from create_payment, get_payment, and lifecycle tools like void_payment or delete_payment.

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 conveys clear usage context: use it for modifying an already-created payment, not creating or reading one, and you must first have the Id and current SyncToken. It does not explicitly name alternatives or say 'use create_payment for new payments', so it stops short of a full when-not statement.

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