8. System tasks
Activities
Each activity type on page 5 is implemented by an activity function in the engine. Activities are the only place the engine calls anything outside itself. Every activity is idempotent on (run id, task reference, attempt): running it twice with the same key has the same effect as once.
| Activity | What it calls | Notes |
|---|---|---|
HttpActivity | Any URL, through the gateway | Also reaches Logic Apps connectors and Document Intelligence. |
JsonActivity | Nothing | JSONPath extraction and object construction. |
LlmActivity | A Foundry model, through the gateway's AI policies | Page 14. |
ToolActivity | The gateway's tool endpoint for the workflow's trust tier | Sends header x-yml-workflow: name@version. Page 14. |
AgentActivity | An agent registered on the gateway, over the A2A protocol | Sends the goal, then polls the agent until it reports a terminal state. Page 14. |
EventActivity | An Event Grid or Service Bus topic | |
QueueActivity | The Service Bus queue for a worker task type | Used internally for WORKER tasks. |
RecordActivity | Azure SQL | Writes run and task history rows. Publishes status events when enabled. |
Output cache
A task with cacheConfig: {key, ttlInSecond} reuses a previous output for the same key within the TTL. For LLM_CHAT the cache is the gateway's semantic cache. For other activities it is the task_cache table in Azure SQL.
Outbound restrictions
HttpActivity calls go through the gateway, which allows only registered destinations. LlmActivity and ToolActivity call only the gateway. No activity opens a connection to an arbitrary address.
Systems without an API
| Need | How |
|---|---|
| A SaaS system such as Xero, SharePoint, Outlook, Dataverse | A Logic Apps Standard workflow with the connector, exposed as an HTTP endpoint, called with HTTP. |
| Text and fields from a PDF or image | Azure AI Document Intelligence, called with HTTP. |
| A business action on the organisation's data | A tool on the action service, called with CALL_TOOL. |
| Anything else | A worker. Page 9. |