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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description adds real context beyond them: output is 'whole-dollar USD', traditional assignments are 'etiquette conventions, not obligations', and the tool 'does not transfer money' – each a meaningful behavioral caveat.

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 tight sentences, front-loaded with the core function before the caveats. Every sentence earns its place, though the 'whole-dollar USD' detail could be folded more economically.

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?

With no output schema, the description usefully characterizes the return shape (percentages plus per-party amounts in whole-dollar USD) and the two parameters are fully schema-documented. Complete enough for an agent to invoke correctly, though the model enum values themselves are only in the schema.

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 both parameters are fully documented in the schema, making 3 the baseline. The description only alludes to the model ('under a selected model') and currency ('USD') without adding format or enum 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?

States a specific verb ('Calculates') and resource ('percentages and amounts for dividing a wedding budget among the couple and their families') with the scope qualifier 'under a selected model'. An agent can distinguish it from get_budget_estimate, but the description never names that or any sibling, so differentiation is left to inference.

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 explains what the tool produces but gives no when-to-use guidance and no alternatives. It clarifies that it does not transfer money, which is a useful exclusion, but there is no signal for choosing this over get_budget_estimate or get_cash_gift_suggestion.

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