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

Annotations already declare readOnlyHint=false and destructiveHint=true, so the safety profile is covered. The description adds meaningful context beyond that: the SyncToken concurrency requirement (updates are rejected against a stale token) and the fact that a new SyncToken comes back, which matters because there is no output schema. It stops short of restating the sparse-vs-full overwrite behavior, though that is covered in the entity schema.

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 the critical preconditions, with the return-value note last. Every clause carries information the agent needs.

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 mutation tool with no output schema, the description covers the essential preconditions and the return contract (saved record plus new SyncToken). It omits any mention of permission requirements or failure modes, but the schema and destructiveHint annotation already carry the overwrite risk, so coverage is close to adequate.

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 parameter already documents Id, SyncToken, sparse semantics, the Line-array replacement rule, and the excluded sensitive fields. The description only echoes the Id/SyncToken requirement, so it adds little beyond the schema and 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 (Update) and resource (an existing payment) scoped to QuickBooks Online, which cleanly separates it from create_payment and delete_payment in the sibling set. It does not, however, explicitly distinguish itself from the near-neighbor void_payment, which is also a mutating operation on a 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 supplies a real prerequisite - 'requires Id and the current SyncToken, as the last search or write returned it' - which implies the agent must call get_payment or search_payments first. But it offers no guidance on when to update versus void or delete a payment, leaving the sibling choice to inference.

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