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

Annotations indicate destructive/write, and the description goes well beyond them: sparse updates by default, full-update clearing behavior, Line array replacement semantics, forbidden sensitive fields, and the retirement-via-Active:false workaround. No contradiction with 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?

The main description is one efficient sentence with the purpose front-loaded. The parameter descriptions are long but necessary to capture QuickBooks-specific semantics; there is no fluff.

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 definition covers all behavioral prerequisites and edge cases (sparse/full updates, lineup handling, no deletion, forbidden fields, company selection). The only gap is absence of an output schema and no mention of the return value, which an agent might need; still, the core information is complete.

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 coverage is 100% and both entity and company have detailed descriptions, so the structured schema already carries the load. The tool's main description only restates the Id/SyncToken requirement already in the entity parameter description; it adds no additional parameter-level meaning.

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?

Description states 'Update an existing customer in QuickBooks Online', which uses a specific verb (update), a specific resource (customer), and a platform. It clearly distinguishes from create_customer and other entity-specific update tools by limiting to existing customers and noting the Id/SyncToken requirement.

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 gives implicit vs explicit guidance: 'existing customer' implies this is not for creation; the entity parameter instructs to fetch the Customer first to get the SyncToken, and notes the workaround for deleting (Active: false, since QuickBooks cannot delete). It doesn't explicitly name sibling alternatives like create_customer or delete_customer, so it stops short of a full 5.

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