--- title: TrUAPI Calls Method Group description: The lifecycle calls a Product uses to identify itself to its Host, the Host capability introduction, and the setup every TrUAPI group relies on. categories: - Apps - Reference url: https://docs.polkadot.com/reference/apps/protocol/truapi/calls/ word_count: 346 token_estimate: 488 version_hash: sha256:8e182299b6d99250add673ec4b388de746954c934be675a6b752083f0acfacd5 last_updated: '2026-06-16T14:17:44+00:00' --- # TrUAPI Calls ## Introduction The TrUAPI Calls method group is the lifecycle handshake between a Product and its Host. When a Product loads, it identifies itself to the Host; the Host responds with the TrUAPI surface the Product is allowed to use. Every other method group sits on top of this one — a Product cannot invoke any capability until the handshake completes. For Product developers, this is mostly implicit. The [`@parity/product-sdk`](https://www.npmjs.com/package/@parity/product-sdk) core handles the handshake in `createApp()` and exposes the resulting `App` object that the rest of the SDK relies on. For Host developers, this is the entry point that every Host implementation has to honor. !!! warning "Provisional" The exact set of lifecycle calls in this group, their names, parameters, and the precise sequencing the Host enforces during Product load are still being finalized. The conceptual contract below is stable; per-call signatures will be added as the surface confirms. ## Conceptual Contract Three things have to happen between a Product loading and that Product being able to use the rest of TrUAPI: - **Product identifies itself**: The Product declares its identity, typically its `.dot` name, so the Host can scope sub-accounts, storage, and topic filters consistently. - **Host advertises capabilities**: The Host responds with the TrUAPI version it implements and the set of method groups available. A Product can branch on the returned capabilities if it needs to support multiple Hosts with different capability sets. - **Product completes setup-time configuration**: The Product configures session-level objects, such as the chain client, storage handle, and signer, against the Host context the lifecycle call returned. After the lifecycle handshake completes, the Product is in steady state: every other call (signing, storage, chat, chain reads) goes through its own method group. ## Where to Go Next
- Learn **Permissions** --- The next layer after the lifecycle handshake: what capabilities the Host will let the Product actually invoke, based on declared and granted permissions. [:octicons-arrow-right-24: Reference](/reference/apps/protocol/truapi/permissions/)