> ## Documentation Index > Fetch the complete documentation index at: https://docs.li.fi/llms.txt > Use this file to discover all available pages before exploring further. # Overview > Author arbitrary DeFi flows as immutable Flow documents, compile them to calldata, and execute them in a single on-chain transaction. The LI.FI Composer API lets you describe a multi-step DeFi operation as a single immutable document called a **Flow**, then compile it into EVM calldata that executes atomically on-chain. A Flow can chain swaps, deposits, approvals, rewards claims, vault zaps, and cross-protocol moves, all through one signed transaction. The Composer API is the **explicit** authoring surface: the `@lifi/composer-sdk` package and the `POST /compose` endpoint. ## What is a Flow? A **Flow** is an immutable JSON document describing: * **Inputs.** The resources (tokens) and scalar values your flow consumes. You pick the input names. * **Calls.** Ordered invocations of named ops (`lifi.swap`, `lifi.zap`, `core.call`, `core.add`, and so on) with typed inputs and outputs. Each call has a user-defined id that downstream calls reference to thread outputs through the flow. * **Guards.** Per-call invariants — slippage floors, equality assertions, and other safety checks — that the VM enforces during execution. Guards are baked into the calldata at compile time; if a guard would fail, the simulation surfaces it before the user signs. * **Refs.** Cross-references between calls, inputs, and runtime context (sender, execution address). You build a Flow with the SDK, pass it to `POST /compose`, and receive `calldata` ready for your wallet to sign. ## Account model Composer never holds your funds in a shared contract. Instead, **each signer gets their own execution proxy**: * **Deterministic.** The proxy address is derived by the proxy factory from the signer's address (CreateX `CREATE3`), so a given signer always maps to the same proxy on a given chain. The SDK exposes it as `builder.context.executionAddress`, and the compile response returns it as `userProxy`. * **You transact with your proxy, not the VM.** The signed transaction's `to` is your proxy (or the proxy factory on the proxy's first use, which deploys it and runs the flow atomically). The proxy `delegatecall`s the shared VM, so the VM's logic runs in your proxy's own storage and balance context — which is exactly why the funds live on the proxy. * **Access-controlled.** Only the signer can drive their own proxy — execution is gated on `msg.sender`, so no one else can run a flow against your proxy or move its balances. * **Funds stay put by default.** During a flow the proxy holds tokens and passes them between steps. Funds **can** leave the proxy — set `sweepTo` to send terminal balances to the signer (or any address) — but if you don't sweep, any remaining balance **stays on the proxy**. That's deliberate: a later flow can pick it up (e.g. with the [`balanceOf`](/composer/composer-api/materialisers/balance-of) materialiser), letting you accumulate or stage funds across submissions. See [Terminal Resources](/composer/composer-api/concepts/sweeping-and-amounts) for how `sweepTo` decides what leaves the proxy, and [Addresses](/composer/composer-api/reference/addresses) for the proxy factory address per chain. ## Machine-readable docs The Composer backend serves its own documentation in two LLM-friendly formats, so AI agents and coding assistants can load the API surface directly. Both are served relative to your Composer base URL (default `https://composer.li.quest`): | Resource | Path | Description | | --------------- | ---------------- | ----------------------------------------------------------------------------------------- | | `llms.txt` | `/llms.txt` | A structured index of the Composer API — sections and links, curated for LLM consumption. | | `llms-full.txt` | `/llms-full.txt` | The full documentation content expanded into a single file. | ## Where to go next Install the SDK and compile your first Flow in five minutes. Flow structure, references, resource model, execution model. Copy-pasteable flows grouped by integrator type.