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

Annotations already declare this as a non-read-only, non-destructive, closed-world write. The description adds genuine value beyond them by disclosing the return shape ('the saved record with its SyncToken'), which matters for chaining an update, and by reinforcing the one-entry-per-account-per-period constraint. It stops short of stating permission requirements or duplicate-budget 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?

Three short sentences, each earning its place: the action, the shape constraint, and the return contract. Nothing is redundant and the core action is front-loaded.

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 create tool with full schema coverage and a rich nested entity object, the description covers action, scope, and return value adequately; the SyncToken mention compensates for the absent output schema. What's missing is permission/precondition context and whether duplicate periods are rejected.

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 parameter is thoroughly documented in the schema itself, so baseline 3 applies. The description restates the ProfitAndLoss and one-entry-per-period constraints but adds no syntax or format detail 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?

States a specific verb and resource ('Create a budget in QuickBooks Online') and narrows scope with 'A profit-and-loss budget with one amount per account per period', which tells an agent exactly which budget shape this tool produces. It does not explicitly name sibling alternatives like update_budget or search_budgets, so it stops short of full sibling differentiation.

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 create semantics make the primary usage self-evident, and the P&L-only constraint implicitly signals other budget types aren't creatable here. However there is no explicit when-to-use guidance, no note on whether a budget already exists for the period, and no pointer to update_budget for modifying an existing budget.

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