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

Annotations already declare readOnlyHint=false, destructiveHint=false and openWorldHint=false, so the mutation safety profile is covered. The description adds one genuinely useful behavioral fact beyond them — that the call returns the saved record including its SyncToken, which matters for subsequent optimistic-concurrency updates — but says nothing about duplicate handling, required fields, or failure behavior.

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 short sentences, front-loaded with the action and followed by the return-value note. Zero filler, though it is thin enough that it reads more like a label than a guide.

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?

There is no output schema, and the description does cover the return value, which is the main gap it needed to fill. However, for a create tool whose payload is a free-form nested object with additionalProperties, it leaves out what happens on duplicate names, whether entity fields are validated, and which fields are practically required.

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 schema itself carries strong parameter semantics (the QuickBooks API v3 Customer shape, the PII prohibition on SSN/tax IDs/birth dates/card data, and the optional company selector). The description adds nothing on top of that, so the baseline 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 ('Create a customer in QuickBooks Online'), which cleanly separates it from create_vendor, create_employee and the other create_* siblings by resource. It stops short of any explicit sibling routing, but the resource is 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?

No guidance on when to use this versus search_customers (to check for an existing customer first) or update_customer (for existing records). The agent must infer that creation is appropriate purely from the tool name.

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