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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds nothing on top — no mention of rounding behavior, currency assumptions, or whether tipPct defaults to zero when omitted.

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?

It is short, but the size reflects under-specification rather than efficiency — there is exactly one fragment and no front-loaded useful content beyond the name. Nothing was trimmed because nothing was ever said.

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 three undocumented parameters, no output schema, and no explanation of the return value (per-person amount? a breakdown including tip?), the description leaves the agent unable to predict results. For a simple calculator this is a low-cost fix that was not made.

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 0% for all three parameters (total, people, tipPct), so the description must compensate and does not. It never mentions that tipPct is optional, what units people/tipPct use, or whether total is pre-tax/pre-tip.

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 is a three-word restatement of the tool name (planning_split_bill → "Split bill calculator"). It conveys the domain but adds no verb-level specificity and does nothing to separate it from near-neighbors like calculate_tip or calculate_discount.

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?

There is no guidance on when to use this versus calculate_tip or percentage, no mention of preconditions, and no statement of what it assumes about the total (pre- or post-tip). The agent must infer everything from the name alone.

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