API Reference

Export	Type	Description
`HCS21Client`	class	Node.js client that inscribes manifests/registry metadata, creates adapter registry topics, publishes declarations, and streams messages via mirror nodes.
`HCS21BrowserClient`	class	Browser/WalletConnect client that can create registry-of-registries layers, publish adapter declarations, and stream messages directly from a user-controlled wallet.
`HCS21BaseClient`	class	Shared base with `buildDeclaration`, `validateDeclaration`, and `fetchDeclarations`.
`AdapterDeclaration`	type	JSON payload that travels over HCS-21 (`p`, `op`, `adapter_id`, `entity`, `package`, `manifest`, optional `manifest_sequence`, `config`, `state_model?`, `signature?`).
`AdapterManifest`	type	Immutable adapter manifest schema for metadata, runtime requirements, capabilities, and consensus bindings (stored via HCS-1 topic or another hashed content store such as IPFS, Arweave, OCI, HTTPS+SRI).
`RegistryMetadataRecord`	type	Optional registry metadata document (HCS-1 topic or other hashed store) referenced in topic memos (`meta` slot).
`ManifestPointer`	type	Result from `inscribeMetadata` with `pointer`, `topicId`, `sequenceNumber`, optional `manifestSequence`, inscription `jobId`/`transactionId`, plus `totalCostHbar` and `costBreakdown` derived from the executed transaction.
`VersionPointerResolution`	type	Result from `resolveVersionPointer` with the latest `declarationTopicId`, metadata, and sequence number.
`AdapterDeclarationEnvelope`	type	Parsed message returned by `fetchDeclarations` (includes `payer`, `consensusTimestamp`, `sequenceNumber`).
`HCS21TopicType`	const	Topic types for memos (`ADAPTER_REGISTRY`, `REGISTRY_OF_REGISTRIES`, `ADAPTER_CATEGORY`).
`buildHcs21CreateRegistryTx`	function	Builds a `TopicCreateTransaction` with the HCS-21 memo format.
`buildHcs21MessageTx`	function	Wraps an `AdapterDeclaration` into a `TopicMessageSubmitTransaction`.
`createRegistryTopic`	method	Creates the HCS-21 adapter declaration topic (`hcs-21:0:<ttl>:0:<meta>`).
`createRegistryDiscoveryTopic`	method	Creates the HCS-2 indexed registry-of-registries topic (`hcs-21:0:<ttl>:1:<meta>`).
`createAdapterCategoryTopic`	method	Creates the HCS-21 adapter-category topic (`hcs-21:0:<ttl>:2:<meta>`).
`createAdapterVersionPointerTopic`	method	Creates the HCS-2 non-indexed pointer topic (`hcs-2:1:<ttl>`) that tracks the live declaration topic for an adapter or registry layer.
`publishVersionPointer`	method	Posts the active HCS-21 topic ID into a version pointer (`hcs-2` message with `t_id`).
`registerCategoryTopic`	method	Registers an adapter category topic inside the discovery topic.
`publishCategoryEntry`	method	Adds an adapter entry (`m = "adapter:<namespace>/<name>"`) pointing to its version pointer topic.
`resolveVersionPointer`	method	Reads the latest message from a version pointer (`hcs-2:1`) to discover the active declaration topic.

Typings

The module ships TypeScript typings. Example:

import type {
  AdapterDeclaration,
  AdapterManifest,
} from '@hashgraphonline/standards-sdk';

These types keep declarations within the 1 KB payload limit and aligned with the HCS-21 specification documented under /docs/standards/hcs-21.

Typings​

Typings