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

Annotations already declare destructiveHint=true and openWorldHint=false, so the safety profile is covered. The description adds genuinely useful behavior beyond that: optimistic-concurrency via SyncToken and the fact that the response carries a new SyncToken the caller must reuse. The richer mutation semantics (sparse updates, Active:false retirement, prohibited fields) live in the schema rather than the description, so no credit for those here.

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 with the prerequisite front-loaded in parentheses and the return value last. Nothing is wasted and no sentence restates the title.

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 usefully previews the return (saved record plus new SyncToken), which the agent needs for chaining. The heavy behavioral detail sits in the parameter schema, which is acceptable, though the description itself could have flagged that updates are sparse by default.

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 nested entity schema already documents Id, SyncToken, sparse semantics, and prohibited fields in depth. The description merely echoes the Id/SyncToken requirement, adding no format or syntax detail beyond the schema. Baseline 3 is appropriate.

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 and resource ("Update an existing class in QuickBooks Online"), which cleanly separates it from create_class, get_class, and search_classes in the sibling list. It never explicitly names an alternative, but the resource noun alone is unambiguous among ~170 siblings.

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 clear prerequisite: the caller needs the Id and the current SyncToken "as the last search or write returned it," which implicitly tells the agent to fetch the record first (get_class/search_classes) before updating. No explicit when-not conditions or alternative routing are stated.

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