PCD Tutorial

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1. Start With A Bounded Requirement

Approve an order only when:
- amount is positive
- limit is positive
- amount does not exceed limit

Otherwise block the order.

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2. Declare Inputs And Output

inputs:
- amount
- limit

output:
- 1 means approve
- 0 means block

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3. Declare Fail-Closed Behavior

amount <= 0 -> 0
limit <= 0 -> 0
amount > limit -> 0
otherwise -> 1

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4. Write The PCD

PC order_risk {
    fn evaluate(amount, limit) {
        if (amount <= 0) {
            return 0;
        }

        if (limit <= 0) {
            return 0;
        }

        if (amount > limit) {
            return 0;
        }

        return 1;
    }
}

• every branch returns a defined value;
• negative or zero inputs block;
• the approval path is the final path;
• no external state is required.

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5. Generate The Starter Candidate

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6. Use Supported Numeric Monomers When The Operation Is Atomic

PC add8_gate {
    fn add8_gate(a: i64, b: i64) -> i64 {
        return MC_00.ADD8(a, b);
    }
}

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7. Agent Checklist

• The requirement is restated in bounded form.
• Inputs and output are named.
• Fail-closed behavior is explicit.
• Every branch returns a value.
• Monomers are selected from the catalog.
• Extended or external behavior is identified before composition.
• The PCD can be reviewed without hidden source context.