# Guide: Declare a Safe Action

**Goal:** add a button that signs a transaction — safely.

Declare the action structurally. The runtime constructs the calldata from your declaration; it can *only* be what
you declared:

```ts
compose.button("Claim", {
  variant: "primary",
  action: { to: "0x<contract>", sig: "claim(uint256)", args: "$amount" },
});
```

At sign time:
```ts
import { buildActionRequest, describeAction, splitArgs } from "@chainrender/client/runtime";
const action = { to: "0x<contract>", sig: "claim(uint256)", args: splitArgs("$amount") };
const tx = buildActionRequest(action, { amount: "1000" });        // calldata = exactly claim(1000)
const human = describeAction(action, { amount: "1000" });         // plain-language for the user to review
```

The enforcer guarantees the declaration is honest (R3–R5): the button can't smuggle a different call, target, or
hidden value. See **[Concepts → Actions & Signing](../concepts/actions.md)**.