discovery: generate capability JSON from the registry

A capability is a descriptor plus what the endpoint declares (device/Capability.ts), and its discovery object is
generated from the two. The new API is bridge.addDevice({ endpointId, name, categories, ... }) and
device.add(PowerController, options): both throw a DeclarationError that names the endpoint, the interface and
the instance (device/validate.ts), and leave the bridge and the device as they were. AlexaInterface is the same
Capability with the 1.x methods on it; it, ActionMapping and the enums moved to src/compat/, Device to src/device/.

What a 1.x caller can observe:
- every endpoint ends with { type: "AlexaInterface", interface: "Alexa", version: "3" } (alexa-interface.html);
  new Alex2MQTT(..., { alexaInterface: false }) leaves it out
- the fields of a capability object come in the order of Amazon's examples; their content is unchanged
- addCapability() with a name that is not an interface throws (1.5.2 announced it with the version "UNKNOWN")
- ActionMapping takes the payload as an object; a JSON string is parsed (1.5.2 sent the string), any other throws
- what Alexa would reject in a 1.x declaration is not refused: device.check() lists it and the bridge logs each
  line once, as "warning: ..." through the log hook, when it answers a discovery
- a device whose JSON cannot be built is left out of the answer and reported as an error event
- PowerController and EndpointHealth are the descriptors and keep ON/OFF and OK/UNREACHABLE; PowerState is new

Tests: six zoo devices declared the 1.x way give the JSON that Alexa accepted from 1.5.2 on 2026-09-28, plus the
Alexa capability. npm test: 85 pass (was 57) in 10-12 s, also on Node 18.20.8 and 20.20.2.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

dist/esm/registry/index.d.ts

@@ -14,7 +14,7 @@ export declare const registry: {
 };
 export { Alexa, BrightnessController, EndpointHealth, PowerController, TemperatureSensor };
 export { DeclarationError, defineInterface } from "./types.js";
-export type { AnyDescriptor, CapabilityExtras, Declared, DirectiveDescriptor, EndpointView, EventDescriptor, InterfaceDescriptor, Label, PropertyDescriptor, } from "./types.js";
+export type { ActionsToDirective, AnyDescriptor, CapabilityExtras, Declared, DirectiveDescriptor, EndpointView, EventDescriptor, InterfaceDescriptor, Label, PropertyDescriptor, Semantics, StatesToRange, StatesToValue, } from "./types.js";
 export { s, SchemaError } from "./schema.js";
 export type { Infer, Schema, Temperature, TimeInterval } from "./schema.js";
 export * from "./catalog.js";

dist/esm/registry/interfaces/stubs.js

@@ -77,6 +77,20 @@ const TABLE = [
     ["Alexa.VideoRecorder", "1", [], "alexa-videorecorder.html"],
     ["Alexa.WakeOnLANController", "1", [], "alexa-wakeonlancontroller.html"],
 ];
+// What 1.5.2 added to the capability object of three of them
+const EXTRAS = {
+    // No properties object; supportsDeactivation and proactivelyReported on the capability itself
+    "Alexa.SceneController": ({ proactivelyReported }) => ({
+        properties: false,
+        topLevel: { supportsDeactivation: true, proactivelyReported },
+    }),
+    "Alexa.ThermostatController": () => ({
+        configuration: { supportedModes: ["HEAT", "COOL", "AUTO", "OFF"], supportsScheduling: false },
+    }),
+    "Alexa.ModeController": ({ options }) => (options.supportedModes?.length > 0
+        ? { configuration: { ordered: true, supportedModes: options.supportedModes } }
+        : {}),
+};
 function kindOf(namespace) {
     if (namespace.endsWith("Sensor"))
         return "sensor";
@@ -94,6 +108,7 @@ function stub([namespace, version, properties, page]) {
         instanced: false,
         properties: Object.fromEntries(properties.map((name) => [name, { name, value: s.unknown() }])),
         directives: {},
+        discovery: EXTRAS[namespace],
     };
 }
 export const STUBS = TABLE.map(stub);

dist/esm/registry/resources.d.ts

@@ -0,0 +1,13 @@
+import type { AssetId } from "./catalog.js";
+import type { Schema } from "./schema.js";
+import type { Label } from "./types.js";
+/** A friendly name as text, in one locale. */
+export declare function text(name: string, locale?: string): Label;
+/** A friendly name from the global Alexa catalog: one id, several names, every language Alexa speaks. */
+export declare function asset(assetId: AssetId): Label;
+/** One friendly name. An asset has to be in the catalog, a text must not be a word Alexa keeps for itself. */
+export declare const label: Schema<Label>;
+/** The friendly names of an instance, a mode or a preset: at least one. */
+export declare const labels: Schema<Label[]>;
+/** What the user is shown for a friendly name: the text, or the id of the asset. */
+export declare function shownAs(name: Label): string;

dist/esm/registry/resources.js

@@ -0,0 +1,39 @@
+// Friendly names: what the user calls an instance, a mode or a preset (resources-and-assets.html).
+import { ASSETS, RESERVED_WORDS } from "./catalog.js";
+import { at, s, SchemaError } from "./schema.js";
+/** A friendly name as text, in one locale. */
+export function text(name, locale = "en-US") {
+    return { "@type": "text", value: { text: name, locale } };
+}
+/** A friendly name from the global Alexa catalog: one id, several names, every language Alexa speaks. */
+export function asset(assetId) {
+    return { "@type": "asset", value: { assetId } };
+}
+const LOCALE = /^[a-z]{2}-[A-Z]{2}$/;
+const textValue = s.object({
+    text: s.string({ min: 1 }),
+    locale: s.string({ pattern: LOCALE, expects: "a locale like en-US" }),
+});
+const assetValue = s.object({ assetId: s.oneOf(ASSETS, "an id of the global Alexa catalog, like Alexa.Setting.Opening") });
+const typed = s.object({ "@type": s.enum("text", "asset"), value: s.unknown() });
+const reserved = RESERVED_WORDS;
+/** One friendly name. An asset has to be in the catalog, a text must not be a word Alexa keeps for itself. */
+export const label = {
+    expects: "a friendly name, from text() or asset()",
+    parse(input, path = "") {
+        const { "@type": type, value } = typed.parse(input, path);
+        if (type === "asset")
+            return { "@type": type, value: assetValue.parse(value, at(path, "value")) };
+        const named = textValue.parse(value, at(path, "value"));
+        if (reserved.includes(named.text.trim().toLowerCase())) {
+            throw new SchemaError(at(path, "value.text"), `${JSON.stringify(named.text)} is a reserved word, not to be used as a friendly name`);
+        }
+        return { "@type": type, value: named };
+    },
+};
+/** The friendly names of an instance, a mode or a preset: at least one. */
+export const labels = s.array(label, { min: 1 });
+/** What the user is shown for a friendly name: the text, or the id of the asset. */
+export function shownAs(name) {
+    return name["@type"] === "text" ? name.value.text : name.value.assetId;
+}

dist/esm/registry/schema.d.ts

@@ -44,6 +44,10 @@ export interface TimeInterval {
     end?: string;
     duration?: string;
 }
+/** The error of a value that is not what a schema expects. */
+export declare function mismatch(path: string, expects: string, input: unknown): SchemaError;
+/** The path of a key of the object at path. */
+export declare const at: (path: string, key: string) => string;
 declare function number(rules?: NumberRules): Schema<number>;
 declare function string(rules?: {
     min?: number;
@@ -54,6 +58,8 @@ declare function string(rules?: {
 declare function boolean(): Schema<boolean>;
 declare function literal<V extends string | number | boolean | null>(value: V): Schema<V>;
 declare function enumeration<V extends readonly string[]>(...values: V): EnumSchema<V[number]>;
+/** One of a list too long to print in an error message: expects says what the list is. */
+declare function oneOf<V extends string>(values: readonly V[], expects: string): EnumSchema<V>;
 declare function unknown(): Schema<unknown>;
 declare function optional<T>(inner: Schema<T>): OptionalSchema<T>;
 declare function nullable<T>(inner: Schema<T>): Schema<T | null>;
@@ -78,6 +84,7 @@ export declare const s: {
     boolean: typeof boolean;
     literal: typeof literal;
     enum: typeof enumeration;
+    oneOf: typeof oneOf;
     unknown: typeof unknown;
     optional: typeof optional;
     nullable: typeof nullable;

dist/esm/registry/schema.js

@@ -19,10 +19,12 @@ function shown(input) {
     const text = JSON.stringify(input) ?? String(input);
     return text.length > 60 ? `${text.slice(0, 57)}...` : text;
 }
-function mismatch(path, expects, input) {
+/** The error of a value that is not what a schema expects. */
+export function mismatch(path, expects, input) {
     return new SchemaError(path, `expected ${expects}, got ${shown(input)}`);
 }
-const at = (path, key) => (path ? `${path}.${key}` : key);
+/** The path of a key of the object at path. */
+export const at = (path, key) => (path ? `${path}.${key}` : key);
 function isRecord(input) {
     return typeof input === "object" && input !== null && !Array.isArray(input);
 }
@@ -65,7 +67,11 @@ function literal(value) {
     return schema(JSON.stringify(value), (input) => input === value);
 }
 function enumeration(...values) {
-    return { ...schema(values.join(" | "), (input) => values.includes(input)), values };
+    return oneOf(values, values.join(" | "));
+}
+/** One of a list too long to print in an error message: expects says what the list is. */
+function oneOf(values, expects) {
+    return { ...schema(expects, (input) => values.includes(input)), values };
 }
 function unknown() {
     return schema("any value", () => true);
@@ -174,6 +180,7 @@ export const s = {
     boolean,
     literal,
     enum: enumeration,
+    oneOf,
     unknown,
     optional,
     nullable,

dist/esm/registry/types.d.ts

@@ -15,6 +15,35 @@ export type Label = {
         assetId: string;
     };
 };
+/** Phrases ("open", "lower") mapped to one directive (alexa-discovery-objects.html, "ActionMappings object"). */
+export interface ActionsToDirective {
+    "@type": "ActionsToDirective";
+    actions: string[];
+    directive: {
+        name: string;
+        payload?: Record<string, unknown>;
+    };
+}
+/** States ("open", "closed") mapped to a value of the property (same page, "StateMappings object"). */
+export interface StatesToValue {
+    "@type": "StatesToValue";
+    states: string[];
+    value: unknown;
+}
+/** States mapped to a range of values of the property. */
+export interface StatesToRange {
+    "@type": "StatesToRange";
+    states: string[];
+    range: {
+        minimumValue: number;
+        maximumValue: number;
+    };
+}
+/** The semantics object of a generic controller: at least one of the two lists. */
+export interface Semantics {
+    actionMappings?: ActionsToDirective[];
+    stateMappings?: Array<StatesToValue | StatesToRange>;
+}
 export interface PropertyDescriptor<V> {
     name: string;
     value: Schema<V>;
@@ -49,7 +78,7 @@ export interface CapabilityExtras {
     properties?: false;
 }
 /** A capability as declared on an endpoint: what discovery() and validate() of its descriptor are given. */
-export interface Declared<O = Record<string, unknown>> {
+export interface Declared<O = unknown> {
     readonly endpointId: string;
     readonly namespace: string;
     /** "" when the interface is declared without an instance. */
@@ -67,7 +96,7 @@ export interface EndpointView {
     readonly friendlyName: string;
     readonly description: string;
     readonly displayCategories: readonly string[];
-    /** The other capabilities of the endpoint. */
+    /** The capabilities declared on the endpoint before this one. */
     readonly capabilities: readonly Declared[];
 }
 export type Properties = Record<string, PropertyDescriptor<any>>;