# Your first contract

> What a contract file holds, with a provider and a consumer of the same endpoint.

A contract file is a YAML document that declares the resources a participant provides, the resources it consumes, and the schemas of their bodies. Both sides of an integration write the same format. The file holds only the declaration: the participant name and the version are flags of `bidirekt publish`, never keys in the file.

## Example

The provider `petstore_api` serves one pet by id:

```yaml
provides:
  rest:
    /pets/*:
      get:
        responses:
          200: Pet

schemas:
  Pet:
    type: object
    properties:
      petId:
        type: integer
      name:
        type: string
```

The consumer `petstore_web` reads that pet, and from it only the name:

```yaml
consumes:
  petstore_api:
    rest:
      /pets/*:
        get:
          responses:
            200: Pet

schemas:
  Pet:
    type: object
    properties:
      name:
        type: string
```

The two files have the same shape. `provides` holds what this participant serves, and `consumes` holds, under each provider's name, what it calls. `schemas` holds the bodies both sides name. The consumer declares only what it reads, so the provider is free to drop `petId`. All three keys are optional, and one file may carry both `provides` and `consumes`: a service in the middle of a chain declares both sides in the same contract.