Register a custom Flow trigger in the Shopify app by defining the trigger schema in the app's Shopify configuration and implementing the flow trigger endpoint that receives a Shopify-signed HTTP POST when an event occurs in the ERP
Define the trigger payload fields that map to ERP-specific events such as purchase order approval or inventory receipt, exposing them as Flow variables available in the workflow builder
Register a custom Flow action endpoint that accepts a Shopify-signed POST with the action payload filled by the merchant in the workflow builder, and implement the corresponding ERP API call within the handler
Implement HMAC signature verification on all incoming Flow trigger and action requests using the shared secret from the app configuration
Return the correct HTTP status codes: 200 for successful action processing, and a 4xx or 5xx to signal to Flow that the action failed and trigger Flow's built-in retry behavior
Surface actionable error messages in the Flow action response body so merchants can debug failed workflow runs from the Flow run history UI
Known gotchas
Shopify Flow custom action endpoints must respond within the timeout window; long-running ERP operations should be processed asynchronously with the initial request returning a 200 and a separate polling or webhook mechanism reporting completion
Flow custom triggers are initiated from the app side by calling the trigger endpoint; the app must store and manage the Shopify shop credentials to know which shop's Flow to trigger when an ERP event occurs
Flow retries failed actions automatically; ERP operations triggered by Flow actions must be idempotent to prevent duplicate purchase orders or inventory adjustments on retry
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claude mcp add --transport http waymark https://mcp.waymark.network/mcp