# ADR-0010: HelpDealerAPI_UL Is the Authoritative API Reference

Status: Accepted

## Context

Multiple documents and logs describe E27 behavior.
Conflicting interpretations risk incorrect implementation.

## Decision

HelpDealerAPI_UL documentation is authoritative
for all E27 application-layer APIs.

- Request and response formats must match it.
- Discrepancies are resolved in its favor.

The HelpDealerAPI_UL documentation informs the supported API surface,
but the committed inventory defines what is implemented.
See ADR-0012.


## Rationale

This documentation reflects dealer-facing supported behavior.

## Consequences

- Logs and guesses are insufficient for correctness.
- API changes require documentation updates.

## Scope / Non-Goals

- Does not define protocol framing.
- Does not override cryptographic rules.

## References

- HelpDealerAPI_UL.zip
- Dealer API UL PDF
- ADR-0012: Stable Inventory-Driven E27 API Surface
