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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint=false, so the safety profile is covered. The description adds genuinely new behavioral context: the output compares 10%-25% tips side by side, and the worked example ('18% on $84 is $15.12') clarifies the input-to-output relationship.

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 with no filler; the capability statement and the comparison feature are front-loaded, followed by the reference URL. The leading worked example is slightly less efficient than leading with the purpose, but nothing is wasted.

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 no-required-param, read-only calculator with no output schema, the description is nearly sufficient: it explains the inputs, the split behavior and the comparison output. It could note the currency default or that all parameters are optional, but nothing essential is missing.

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 bill, tip, people and currency are already fully documented in the schema. The description mentions bill, percentage and split but omits the currency parameter and adds no syntax or range 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?

The description states a specific action (compute a tip, split a bill) with a concrete worked example, so the purpose is unambiguous. It does not explicitly distinguish itself from nearby siblings such as percentage_calculator or discount_calculator, but the name and scenario make the resource clear.

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?

Usage is implied by the described scenario ('Enter the bill, pick a percentage and split the total'), which tells the agent when this is relevant. There is no explicit when-not guidance and no named alternative among the many sibling calculators.

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