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

Annotations already establish this as a safe, idempotent, non-destructive read. The description adds useful computation details: rounding down, organizer covering the remainder, currency, and mutual exclusivity of the two amount inputs.

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?

The description is compact and front-loaded, presenting the main split behavior first and the alternative mode second. Every sentence carries useful information with no redundant restatement.

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 still explains what each mode returns: either the per-person contribution after rounding or the total budget. That is sufficient for a low-complexity calculation tool whose annotations cover safety.

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 coverage is 100%, so the schema already documents the three parameters. The description adds the important exactly-one constraint between giftCost and perPerson and clarifies how payers affects the division, going beyond the schema text.

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 states the resource and both operations precisely: splitting a group gift per payer with rounding, or deriving total budget from a per-person amount. An agent can identify the calculation without inspecting the schema.

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 clearly says to pass exactly one of giftCost or perPerson, which resolves the main invocation ambiguity. It does not name alternatives, but the sibling tools are unrelated, so there is no meaningful routing choice to explain.

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