Glossary

Term	Meaning
Action service	The service that performs business actions on the organisation's data. Reached through the gateway as tools.
Activity	A function in the engine that performs one activity task type.
A2A	Agent2Agent, the protocol used to send a goal to an external agent and follow it to completion.
Agent	A model that decides step by step what to do. Written in this engine as a loop of tasks, or hosted elsewhere and called with CALL_AGENT.
App Configuration	Azure service for non-secret settings. Source of ${workflow.env.*}.
Archive	Finished runs past retention, stored as JSON files in Blob.
Correlation id	A caller-supplied id for finding related runs.
Dead-letter queue	Where a queue message goes after its delivery attempts are exhausted.
Decider	The class that, given a definition and completed tasks, returns the next task.
Definition	See workflow definition.
Domain	A label on a start request that routes worker tasks to a separate queue and worker pool.
DTS, Durable Task Scheduler	Azure service that stores each run's live state and resumes it after interruption.
External agent	An agent hosted outside the engine, registered on the gateway, called as one step.
Event handler	A stored rule that turns an incoming message into a start or a task completion.
Event Grid	Azure service for discrete events.
Event Hubs	Azure service for high-volume streams.
Fabric	The organisation's analytics platform. Receives a mirror of the history tables.
Foundry	Azure service that provides AI models.
Gateway	API Management. Authenticates callers, exposes tools, applies AI policies.
History	The Azure SQL rows describing runs and tasks.
Human gate	A HUMAN task: the run waits for a posted decision.
Idempotency key	A caller-supplied key that prevents duplicate runs.
Instruction registry	Versioned texts used as model instructions, referenced as ${instructions.name@version}.
Interpreter	The WorkflowInterpreter orchestration that runs every definition.
Key Vault	Azure service for secrets. Source of ${workflow.secrets.*}.
Logic Apps	Azure service with connectors to SaaS systems. Called with HTTP.
MCP	The protocol the gateway uses to expose tools to models and workflows.
Payload offload	Storing large inputs and outputs in Blob and keeping the URL in the record.
Poll	A worker asking the Task API for waiting tasks.
Queue	A Service Bus queue holding waiting tasks for one task type.
Run	One execution of a workflow definition with one input.
Schedule	A cron rule that starts runs.
Service Bus	Azure messaging service. Holds worker queues and topics.
System task	A task the engine performs itself: interpreter and activity types.
Task	One step of a definition.
Task definition	Settings for one task type: timeouts, retries, limits, schemas.
Task reference	The unique name of a task inside a definition.
Task type	The kind of a task: HTTP, HUMAN, WORKER, and so on.
Tool	An action exposed through the gateway. Grouped in trust tiers.
Trust tier	Read, write, or high-risk. Determines the gate rule for a tool.
Worker	A program that polls for worker tasks, runs them, and posts results.
Worker task	A task performed by a worker.
Workflow definition	The versioned JSON document that describes a workflow.