# A2UICore v0.1.1 - API Reference

## Modules

- [A2UICore.Catalog.Document](A2UICore.Catalog.Document.md): Reads a catalog document into the parts of an `A2UICore.Catalog`
(`parse/2`) and writes those parts back as a document (`build/1`), so
that `build(parse(document))` equals `document`, apart from the
components and functions that `$defs.anyComponent` /
`$defs.anyFunction` leave out.
- [A2UICore.Catalog.MCP](A2UICore.Catalog.MCP.md): The A2UI MCP catalog, ready to evaluate: the catalog through which a
surface calls [Model Context Protocol](https://modelcontextprotocol.io)
tools.
- [A2UICore.Catalog.Refs](A2UICore.Catalog.Refs.md): `$ref` handling for catalog documents.
- [A2UICore.Catalog.SchemaCleaner](A2UICore.Catalog.SchemaCleaner.md): Normalizes the schema nodes a catalog's validation schema is assembled
from, as the reference catalog does before bundling common types
- [A2UICore.Catalog.ValidationSchema](A2UICore.Catalog.ValidationSchema.md): Builds a catalog's validation schema: the self-contained JSON Schema
messages are validated against (the reference's
`Catalog.validation_schema`).
- [A2UICore.Functions.MCP](A2UICore.Functions.MCP.md): Implementations of the MCP catalog's functions (see
`A2UICore.Catalog.MCP`).
- [A2UICore.JMESPath](A2UICore.JMESPath.md): [JMESPath](https://jmespath.org/specification.html) queries over JSON
data: the engine behind the MCP catalog's `jmespath` function.
- [A2UICore.KeyOrder](A2UICore.KeyOrder.md): JSON values whose objects keep their key order, as
`Jason.OrderedObject`s, for writing a document in a given order:
`Jason.encode!/1` writes an ordered object's keys in order, and a
map's in the map's own order.
- [A2UICore.MCP](A2UICore.MCP.md): Reading A2UI out of [Model Context Protocol](https://modelcontextprotocol.io)
values: the A2UI messages a tool result or a resource carries, the UI
resources a tool or a result names, and the MCP Apps a resource holds.
- [A2UICore.MCP.Client](A2UICore.MCP.Client.md): A connection to a [Model Context Protocol](https://modelcontextprotocol.io)
server, as the MCP catalog's functions use it.
- [A2UICore.Validation.NestedCalls](A2UICore.Validation.NestedCalls.md): Checks the function calls nested in a v1.0 `updateComponents` batch
against the catalogs they run in, before anything is committed.

- Processing
  - [A2UICore](A2UICore.md): Elixir implementation of the [A2UI protocol](https://a2ui.org/) core engine:
versioned message envelopes, catalog schemas, surface state, data model,
and processing of agent-to-renderer updates.
  - [A2UICore.Error](A2UICore.Error.md): The single error struct used across the A2UI packages.
  - [A2UICore.Error.Detail](A2UICore.Error.Detail.md): A single structured diagnostic entry attached to an `A2UICore.Error`.

  - [A2UICore.Processor](A2UICore.Processor.md): Applies agent→renderer messages to a set of surfaces.
  - [A2UICore.RPC](A2UICore.RPC.md): The function RPC of protocol v1.0, as a value.

- Messages
  - [A2UICore.Message](A2UICore.Message.md): Wire messages: decode raw agent→renderer payloads into canonical
`A2UICore.Message.Operation` structs, and encode operations back to
wire-format maps.
  - [A2UICore.Message.Adapter](A2UICore.Message.Adapter.md): Version adapter behaviour and the shared envelope-extraction pipeline.
  - [A2UICore.Message.AdapterRegistry](A2UICore.Message.AdapterRegistry.md): Resolves version adapters from version strings and raw payloads — a
faithful port of the reference `VersionAdapterFactory`, including
its error detail paths (`messages.0.version`, …).
  - [A2UICore.Message.Operation](A2UICore.Message.Operation.md): Version-neutral operations: what `A2UICore.Message.decode/2` returns
and `A2UICore.Processor.apply_operations/3` applies.
  - [A2UICore.Message.Operation.AgentFunctionResponse](A2UICore.Message.Operation.AgentFunctionResponse.md): An `agentFunctionResponse` message (v1.0): the agent's answer to the
renderer's call `function_call_id`, either a `value` or an `error`
map with `"code"` and `"message"`.

  - [A2UICore.Message.Operation.CallRendererFunction](A2UICore.Message.Operation.CallRendererFunction.md): A `callRendererFunction` message (v1.0): the agent asks the renderer
to run function `call` with `args`, from the catalog `catalog_id`,
in the context of surface `surface_id` (or of no surface when `nil`).
The answer must carry `function_call_id`.

  - [A2UICore.Message.Operation.CreateSurface](A2UICore.Message.Operation.CreateSurface.md): A `createSurface` message: a new surface, the catalog it uses
(`catalog_id`) and whether the renderer sends its data model back
(`send_data_model`). `theme` is kept for v0.9 messages only. A v1.0
message may carry the surface's first `components` and `data_model`.

  - [A2UICore.Message.Operation.DeleteSurface](A2UICore.Message.Operation.DeleteSurface.md): A `deleteSurface` message.

  - [A2UICore.Message.Operation.UpdateComponents](A2UICore.Message.Operation.UpdateComponents.md): An `updateComponents` message: components to add to a surface or
replace in it, as the wire maps.

  - [A2UICore.Message.Operation.UpdateDataModel](A2UICore.Message.Operation.UpdateDataModel.md): An `updateDataModel` message: `value` written at `path` (the root by
default) of a surface's data model. A `nil` value deletes.

  - [A2UICore.Message.RendererToAgent](A2UICore.Message.RendererToAgent.md): Builders for the messages a renderer sends to the agent
(`renderer_to_agent.json`)

- Catalogs
  - [A2UICore.Catalog](A2UICore.Catalog.md): A versioned set of component and function definitions: the model of a
catalog document.
  - [A2UICore.Catalog.Basic](A2UICore.Catalog.Basic.md): The basic catalog of a protocol version, ready to evaluate.
  - [A2UICore.Catalog.Component](A2UICore.Catalog.Component.md): A component a catalog declares: the name a message uses and its JSON
Schema as the catalog document writes it (with its `allOf` mixins and
references), plus the v1.0 composition constraints (`allowedParents`,
`allowedChildren`).
  - [A2UICore.Catalog.Function](A2UICore.Catalog.Function.md): A function a catalog declares: its schema plus, when the catalog can
evaluate it, an implementation.
  - [A2UICore.Catalog.RefSpec](A2UICore.Catalog.RefSpec.md): Which properties of a component refer to other components, and how to
pull those references out of a component's properties.
  - [A2UICore.Catalog.ReferenceMap](A2UICore.Catalog.ReferenceMap.md): Derives, from a catalog's component schemas, which properties are
child references — the data `A2UICore.Catalog.RefSpec` extracts from.
  - [A2UICore.Formatter](A2UICore.Formatter.md): Locale-sensitive formatting for the basic catalog's `formatNumber`,
`formatCurrency`, `formatDate` and `pluralize` functions.
  - [A2UICore.Formatter.Default](A2UICore.Formatter.Default.md): The built-in `A2UICore.Formatter`: `en-US` conventions for every locale.
  - [A2UICore.Functions.Basic](A2UICore.Functions.Basic.md): Implementations of the basic catalog's functions.
  - [A2UICore.Functions.System](A2UICore.Functions.System.md): Functions the runtime supplies to every catalog: the `@` namespace.

- State
  - [A2UICore.State.Component](A2UICore.State.Component.md): One component instance on a surface: its id, catalog type, and
properties.
  - [A2UICore.State.Components](A2UICore.State.Components.md): The set of components on a surface, keyed by id.
  - [A2UICore.State.DataModel](A2UICore.State.DataModel.md): The reactive JSON data store behind a surface — an immutable port of
the reference `DataModel` (RFC 6901 pointers, auto-vivifying writes,
cascading change notifications).
  - [A2UICore.State.Surface](A2UICore.State.Surface.md): The state of one UI surface: its identity, catalog selection, theme,
data model and components.
  - [A2UICore.State.SurfaceGroup](A2UICore.State.SurfaceGroup.md): All live surfaces of a session, keyed by surface id.

- Resolution
  - [A2UICore.Accessibility](A2UICore.Accessibility.md): What a component tells assistive technology.
  - [A2UICore.Expression](A2UICore.Expression.md): Parser for A2UI expression templates — the `${…}` interpolation
language used by `formatString` and by dynamic string values.
  - [A2UICore.Resolution.Action](A2UICore.Resolution.Action.md): An action property of a resolved component.
  - [A2UICore.Resolution.Binder](A2UICore.Resolution.Binder.md): Resolves a component's properties to the values a renderer displays.
  - [A2UICore.Resolution.Binding](A2UICore.Resolution.Binding.md): A resolved dynamic property: the value it currently holds and, when the
component bound it to a data path, the absolute path a write goes to.
  - [A2UICore.Resolution.DataContext](A2UICore.Resolution.DataContext.md): A data-binding scope: the absolute path relative bindings resolve
against, the collection-template iteration index, and — when built
for a surface — what is needed to evaluate dynamic values.
  - [A2UICore.Resolution.Node](A2UICore.Resolution.Node.md): One mounted position of a resolved component tree.
  - [A2UICore.Resolution.NodeResolver](A2UICore.Resolution.NodeResolver.md): Resolves a surface's flat component dictionary into a tree of
`A2UICore.Resolution.Node`s.

- Validation
  - [A2UICore.CommonTypes](A2UICore.CommonTypes.md): Validates values against the protocol's shared type definitions — the
`$defs` of each version's `common_types.json` (`DynamicValue`,
`FunctionCall`, `ChildList`, `Action`, v1.0 `Extensions`, …).
  - [A2UICore.Schema](A2UICore.Schema.md): JSON Schema **Draft 2020-12** validator used by A2UI's catalog,
envelope, and payload validation.
  - [A2UICore.Schema.ECMA262](A2UICore.Schema.ECMA262.md): ECMA-262 → PCRE regex translation for the `pattern` and
`patternProperties` keywords.
  - [A2UICore.Schema.Source](A2UICore.Schema.Source.md): Loads the A2UI protocol's own JSON Schema documents — vendored under
`priv/` from a pinned revision of the specification — plus the shipped
basic catalogs.
  - [A2UICore.Validation.ComponentsUpdate](A2UICore.Validation.ComponentsUpdate.md): Validates a batch of incoming components against the surface they
update, before any of them is committed.
  - [A2UICore.Validation.Config](A2UICore.Validation.Config.md): Options controlling how strictly a component graph and its payloads
are validated — the reference `ValidationConfig`.
  - [A2UICore.Validation.Integrity](A2UICore.Validation.Integrity.md): Payload preflight checks that run before schema validation:
global nesting depth, nested function-call depth, and JSON-pointer
path syntax. Ported verbatim from the reference's
`validate_recursion_and_paths`.
  - [A2UICore.Validation.Payload](A2UICore.Validation.Payload.md): Validates component, function-call and theme payloads against a
catalog.
  - [A2UICore.Validation.ReservedKeys](A2UICore.Validation.ReservedKeys.md): The v1.0 reserved-key rule for dynamic objects.
  - [A2UICore.Validation.Topology](A2UICore.Validation.Topology.md): Component-graph validation: root presence, dangling references,
self-references, cycles, depth, unreachable components, and catalog
composition constraints.

- Primitives
  - [A2UICore.Coerce](A2UICore.Coerce.md): Value coercions shared by the catalog functions: truthiness, text and
number conversion.
  - [A2UICore.Identifier](A2UICore.Identifier.md): UAX #31 identifier validation for catalog entity names, with the
upstream pattern `^[\p{XID_Start}_][\p{XID_Continue}]*$`, compiled
like a schema pattern by `A2UICore.Schema.ECMA262`: exact on
Erlang/OTP 28 and later, an approximation on older PCRE.
  - [A2UICore.Pointer](A2UICore.Pointer.md): RFC 6901 JSON Pointer parsing, building, and resolution.
  - [A2UICore.SemVer](A2UICore.SemVer.md): Semantic Versioning 2.0.0 parsing and comparison.
  - [A2UICore.Version](A2UICore.Version.md): A2UI protocol-version registry and catalog compatibility rules.