# Contracts

This section covers Market 2.0 contract integration for product developers and contract integrators.

## Contract Development Basics

When designing a contract to integrate with Curio:

1. Prefer read-only verification interfaces for deal checks.
2. Use explicit interface versioning.
3. Keep verification input and deal-state semantics stable and deterministic.
4. Use a deterministic not-found contract error for missing deal references.
5. Treat provider allowlisting as a separate operational policy.

## DDO

Current DDO integration uses:

1. [CurioDealView v1](/market-2.0/contracts/curiodealview.md)
2. [DDO contract review and allowlisting](/market-2.0/contracts/ddo-contract-review.md)

Future products can add their own contract interfaces without changing the top-level Market 2.0 deal envelope.


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