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

Annotations already mark the tool as read-only, idempotent, and non-destructive, so the safety profile is covered. The description adds useful behavioral context by stating what it returns: the tip amount, total, and per-person share. No contradiction with annotations.

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 short, front-loaded with the action, and every sentence contributes value. The source URL is a minor extra that does not detract from clarity or add significant noise.

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 simple calculator with full schema coverage, output schema, and safety-bearing annotations, the description is complete. It explains the purpose, optional split behavior, and the exact return values, which is sufficient for an agent to invoke it correctly.

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%, with all three parameters (bill, split, tipPercent) already described in the schema. The description does not add parameter-specific semantics beyond what the schema provides, so the baseline score of 3 is appropriate.

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 uses a specific verb and resource ('Work out a tip on a bill') and clearly states the optional split behavior. It is unambiguous and distinct from the large sibling set of calculators, especially since 'tip' is the core resource and the output items are named.

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 makes the usage context clear: use it to calculate a tip and optionally split the total. It does not explicitly mention alternatives like hopi_bill_splitter or state when not to use the tool, so it falls short of the 'explicit alternatives/exclusions' bar.

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