> ## Documentation Index
> Fetch the complete documentation index at: https://docs.brik64.com/llms.txt
> Use this file to discover all available pages before exploring further.

# PCD Authoring Rules

> PCD rules for AI agents.

Write PCD that a human can review as a circuit.

## Required Shape

```pcd theme={null}
PC example {
    fn evaluate(input) {
        if (input <= 0) {
            return 0;
        }

        return 1;
    }
}
```

## Rules

* Start with `PC <name>`.
* Use explicit functions.
* Name inputs in plain language.
* Return from every path.
* Keep fail-closed behavior visible.
* Use catalog monomer names only.
* Avoid invented dialect features.
* Explain external behavior before using extended monomers.

## Review Before Reporting

```text theme={null}
PCD file:
Circuit name:
Inputs:
Output:
Fail-closed behavior:
Monomers:
EVA structure:
Evidence status:
```

If any item is unknown, report it as unknown instead of filling it in from assumption.