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

Annotations already carry readOnlyHint=false and destructiveHint=true, so the description does not need to restate that this mutates data. The description adds only the Id/SyncToken prerequisite and no side-effect detail such as reversibility or what a full update clears; those details live in the parameter schema rather than the tool description.

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?

A single sentence front-loads the verb and resource and tucks the essential prerequisite into a parenthetical. There is no filler, redundancy, or unnecessary background.

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?

Between the rich entity schema, the company-field description, and the destructive/readOnly annotations, an agent has enough information to invoke this tool correctly even without an output schema. The main missing piece is explicit sibling routing, which is already a usage-guideline gap.

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 description thoroughly explains required fields, sparse vs full updates, Line-array replacement, and sensitive-data exclusions. The tool description only restates the Id/SyncToken requirement, adding no new parameter semantics beyond what the schema already provides.

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?

The description names a specific verb ('Update'), a specific resource ('credit memo'), and the domain ('QuickBooks Online'). The qualifier 'existing' plus the Id/SyncToken requirement clearly scopes the tool to modifying an already-created memo rather than creating, deleting, or sending one.

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 a clear usage context: use this tool when you need to change an existing credit memo, and the entity schema reinforces fetching the CreditMemo first to get the current SyncToken. It does not explicitly name alternative tools or give when-not-to-use conditions, so it stops short of full routing guidance.

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