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

Annotations already declare destructiveHint=true and readOnlyHint=false, so the safety profile is covered. The description adds genuinely useful non-annotation context: optimistic concurrency via SyncToken and the fact that the saved record is returned with a new SyncToken, which matters for chained updates.

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 tightly packed sentences with no filler. The concurrency requirement and return behavior are front-loaded and each clause 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 mutation tool with a nested entity object and no output schema, the description briefly covers the return value and the key prerequisite, while the schema carries the complex sparse-update semantics. Combined, an agent has enough to invoke correctly, though it could note the sparse-by-default behavior more visibly.

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 entity and company parameters are already fully documented in the schema, including sparse-update rules and required fields. The description only restates the Id/SyncToken requirement already present in the schema, adding no new syntax or format detail.

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 transfer in QuickBooks Online), making it trivially distinguishable from siblings like create_transfer, get_transfer, delete_transfer, and search_transfers. An agent knows exactly which operation this performs.

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?

Gives a concrete prerequisite — requires the Id and the current SyncToken as returned by the last search or write — which implicitly routes the agent through a fetch/search first. It does not, however, explicitly name alternatives or state when-not-to-use this tool versus a full-overwrite path.

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