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

Annotations already declare destructiveHint=true and readOnlyHint=false, yet the description adds two useful behaviors: the optimistic-concurrency SyncToken requirement and the fact that the saved record plus a new SyncToken comes back. It does not warn that omitting fields left out can be cleared (that lives in the schema's sparse semantics).

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 sentences, front-loaded with the action, then the prerequisite, then the return value. Nothing is wasted and no filler is present.

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?

No output schema exists, so the description's note about returning the saved record with its new SyncToken is exactly the missing piece an agent needs. Combined with the schema's sparse-update rules and the destructive annotation, the definition is essentially complete, though the SyncToken prerequisite is only stated once and could be reinforced as a hard requirement.

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 fully documented in the schema, including sparse semantics and the SyncToken/PII rules. The description's mention of Id and SyncToken is a helpful restatement but adds no syntax or format detail beyond what the schema provides, 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 ("Update an existing journal entry") and scopes it to QuickBooks Online, so it is clearly distinguishable from sibling update_* tools by resource. It does not, however, explicitly differentiate itself from create_journal_entry, get_journal_entry, or delete_journal_entry beyond the verb.

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?

It gives a real prerequisite (Id plus the current SyncToken, as returned by the last search or write), which implies the fetch-then-update workflow. It never states when to choose this over alternatives such as create_journal_entry or search_journal_entries, nor any when-not conditions.

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