Source: https://guthlabs.ai/docs/instruments/tip-calculator/implementation/

instrument implementation / implementation-contract

# Tip Calculator implementation

A source-bound implementation contract for Tip Calculator; deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-clean

**Evidence ID**: t5-112

**Effect**: Computation or source lookup only

## Input and validation requirements

A split count of zero produces an undefined tip-per-person result and must be rejected. The round-up branch is also not fully defined by the specification because it does not state whether rounding applies to the total, tip, or another currency increment.

## Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "inputs": {
    "bill_amount": 27.8,
    "tip_percent": 20,
    "round_up": false,
    "split_count": 2
  },
  "expected_outputs": {
    "tip": 5.56,
    "total": 33.36,
    "tip_per_person": 2.78
  },
  "working": "Convert 20% to 0.20. Tip = 27.80 × 0.20 = 5.56. Total = 27.80 + 5.56 = 33.36. Tip per person = 5.56 ÷ 2 = 2.78."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/tip-calculator/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/tip-calculator/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/tip-calculator/qualification/>)

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json`

- `evidence-tranche5/tranche5-results.json`