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

Annotations already declare readOnlyHint=false and destructiveHint=true, and the description adds meaningful behavior beyond them: the optimistic-concurrency requirement (Id + current SyncToken) and the fact that the saved record is returned with a new SyncToken. It does not mention error behavior on stale tokens or side effects on linked transactions.

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?

Two tight sentences, front-loaded with the action and immediately followed by the prerequisite and return behavior. No filler.

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 two-parameter mutation with a very rich nested schema and destructive/readOnly annotations already present, the description supplies the missing pieces: the concurrency prerequisite and the return value (helpful since there is no output schema). Coverage is essentially complete, though it could note how failures on stale SyncTokens are surfaced.

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 documents Id, SyncToken, sparse-update semantics, sparse:false clearing behavior, and the required Amount/BankAccountRef/CreditCardAccountRef repeats. The description only restates the Id/SyncToken requirement, adding no syntax or format detail beyond the schema, so the baseline 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?

States a specific verb+resource ('Update an existing credit card payment txn in QuickBooks Online'), which cleanly separates it from create_, delete_, get_, and search_ siblings for the same entity. It does not explicitly name the alternatives, but the resource specificity makes its role 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?

Provides the key prerequisite: the record must exist and the caller needs Id plus the current SyncToken 'as the last search or write returned it', which tells the agent to fetch first via search_credit_card_payment_txns or a prior write. It gives no explicit when-not guidance or named alternatives, so it stops short of a 5.

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