# Creating Internal and External SDKs
Source: https://speakeasy.com/docs/sdks/guides/overlays/internal-external-versions

To create two different versions of an SDK, one for internal use and one for external use, use JSONPath expressions in [OpenAPI Overlays](/openapi/overlays) (a standard extension for modifying existing OpenAPI documents without changing the original). This approach dynamically targets and hides internal operations and parameters from the public SDK. The [`workflow.yaml` file](/docs/workflow-file-reference) can be configured to include Overlays as part of the source definition.

### Using the `x-internal` Extension

First, add an `x-internal: true` extension to all the operations, parameters, and other elements in the OpenAPI spec that should only be available in the internal SDK.

```yaml filename="api.yaml"
info:
  title: Sample API
  version: 1.0.0
  description: A sample API with internal paths and parameters.

paths:
  /public-resource:
    get:
      summary: Retrieve public data
      responses:
        '200':
          description: Public data response
          content:
            application/json:
              schema:
                type: object
                properties:
                  id:
                    type: string
                  name:
                    type: string

  /internal-resource:
    x-internal: true   # This path is internal and should not be exposed externally
    get:
      summary: Retrieve internal data
      responses:
        '200':
          description: Internal data response
          content:
            application/json:
              schema:
                type: object
                properties:
                  id:
                    type: string
                  internalInfo:
                    type: string
                    description: Internal information
                    x-internal: true  # This field is internal
        description: "This endpoint is restricted for internal staff management and not visible in public SDKs."
```

### Using JSONPath Expressions in an Overlay

Next, use a JSONPath expression to remove all the internal paths and parameters from the SDK. This removal occurs specifically when generating the internal SDK.

```yaml filename="internal-overlay.yaml"
info:
  title: Sample API Overlay
  version: 1.0.0
actions:
  - target: $.paths.*.*[?(@["x-internal"] == true)]
    remove: true
  - target: $.paths.*.*[?(@.properties[?(@["x-internal"] == true)])]
    remove: true
```

Define a workflow that generates both the internal and external SDKs.

```yaml filename="workflow.yaml"
workflowVersion: 1.0.0
speakeasyVersion: latest
sources:
  external-api:
    inputs:
      - location: ./api.yaml
    overlays:
      - location: ./external-overlay.yaml
  internal-api:
    inputs:
      - location: ./api.yaml
    overlays:
      - location: ./internal-overlay.yaml
targets:
  internal-sdk:
    target: python
    source: internal-api

  external-sdk:
    target: python
    source: external-api
```