Core Primitives

iii has three top-level primitives:

• Function: a named unit of work such as orders::validate
• Trigger: an event source bound to a function
• Worker: a process that connects to the engine and executes functions

Since 0.25 every function is also observable: iii.observe(source, target) invokes target on each invocation of source that passes its filters. Observers replace trigger bindings over time; the built-in providers (http, cron, queue, state, stream, pub/sub, database) still use trigger types in 0.25, so keep registerTrigger for them. See iii-observe.

Use :: in function IDs, leading slashes in HTTP api_path, and expression for cron config.

Function Registration

Register local handlers when you control the implementation. Register HTTP-invoked functions when iii should call an existing external endpoint.

Shape	Use for
registerFunction(id, handler, options?)	Local worker code
registerFunction(id, HttpInvocationConfig, options?)	Existing HTTP services
registerTrigger({ type, function_id, config, metadata? })	Binding a built-in event source (deprecated in 0.25, still required for providers that have not migrated)
observe({ function_id, args?, filters? }, target, options?)	Running target after another function's invocations, or on an engine event (iii-observe)
trigger({ function_id, payload, action?, timeout? })	Calling any function by ID

Functions and triggers can carry metadata for ownership, discovery, and generated skills. Do not put secrets in metadata.

Workers and Registry

A worker is any process that connects to the engine and registers functions or trigger types. There are two common paths: