Create Your Own Transformer

Build custom transformers for validation, enrichment, or redaction.

The transformer interface

Transformers are functions that receive a context object and return a transformer instance:

The context contains:

The returned instance must implement:

Return values

Return	Behavior
`event`	Continue chain with modified event
`void`	Continue chain, event unchanged
`false`	Stop chain, event dropped

Minimal example

Push context

The push function receives an event and a push context:

config: Transformer configuration
env: Environment dependencies
logger: Scoped logger for output
id: Transformer identifier
collector: Access to collector instance
ingest: Request metadata from source (optional)

Examples

Enrich: add server-side data

Validate: custom check

Using your transformer

Testing

Package convention

Every walkerOS package includes machine-readable metadata for tooling and discovery.

`walkerOS` field in package.json

Field	Required	Description
`walkerOS`	Yes	Object with `type` metadata (and `platform` for sources/destinations)

Build-time generation

Use buildDev() from the shared tsup config to auto-generate walkerOS.json:

This file contains your package's JSON Schemas and examples, enabling MCP tools and the CLI to validate configurations without installing your package.

Publishing checklist

walkerOS field in package.json
Keywords include walkeros and walkeros-transformer
buildDev() in tsup.config.ts
dist/walkerOS.json generated on build
npm run test passes
npm run lint passes

Next steps

Review Validator source as reference
Learn about creating sources
Learn about creating destinations

💡 Need Professional Support?

Need professional support with your walkerOS implementation? Check out our services.

The transformer interface​

Return values​

Minimal example​

Push context​

Examples​

Enrich: add server-side data​

Validate: custom check​

Using your transformer​

Testing​

Package convention​

walkerOS field in package.json​

Build-time generation​

Publishing checklist​

Next steps​