> For the complete documentation index, see [llms.txt](https://fifo-docs.gitbook.io/colibri/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://fifo-docs.gitbook.io/colibri/getting-started/contract-call.md).

# Read and invoke a contract

Use this guide with a deployed Hello World contract exposing `hello(to: string)` on Testnet, such as the contract in the [Colibri examples](https://github.com/fazzatti/colibri-examples). Contract IDs are network-specific, and Testnet resets can remove old deployments; this guide does not assume an old shared deployment still exists.

```sh
deno add jsr:@colibri/core
CONTRACT_ID=YOUR_DEPLOYED_CONTRACT_ID deno run --allow-net --allow-env=CONTRACT_ID hello.ts
```

```ts
import { Contract, NetworkConfig } from "@colibri/core";

const contractId = Deno.env.get("CONTRACT_ID");
if (!contractId) {
  throw new Error("Set CONTRACT_ID to your Testnet Hello World contract");
}
const contract = new Contract({
  networkConfig: NetworkConfig.TestNet(),
  contractConfig: { contractId },
});

// A method name and named arguments require the contract specification.
await contract.loadSpecFromNetwork();
const greeting = await contract.read({
  method: "hello",
  methodArgs: { to: "World" },
});
console.log(greeting);
```

`read()` simulates and decodes the result using the loaded spec. It does not submit a transaction or persist changes. A successful read is not evidence that a later write will succeed: state and authorization can differ.

See [reading and invoking](/colibri/colibri-core/contract/invocation.md) for both call shapes and [validated values](/colibri/colibri-core/contract/values.md) for optional argument validation.

## Submit a write

With the funded signer and network setup from the [payment quick start](/colibri/getting-started/quick-start.md), replace the read with the following fragment:

```ts
const result = await contract.invoke({
  method: "hello",
  methodArgs: { to: "World" },
  config: {
    source: sender.publicKey(),
    signers: [sender],
    fee: { max: "1000000" },
    timeout: 30,
  },
});
console.log(result.hash, result.returnValue);
```

The example cap is 1,000,000 stroops (0.1 XLM), not a guarantee of actual cost. Assembly fails if the simulated resources leave insufficient inclusion fee. Network conditions and the method's resources determine whether the cap works. For real application writes, choose the cap intentionally using [TransactionConfig fee strategies](/colibri/colibri-core/transaction-config.md#fee-strategies). Use [resource controls](/colibri/colibri-core/transaction-config/resources.md) when adjusting the Soroban budgets.

Use `readRaw()`/`invokeRaw()` or the pipeline factories when you already have encoded ScVal arguments. See [contract configuration](/colibri/colibri-core/contract/configuration.md), [deployment](/colibri/colibri-core/contract/deployment.md), and [the invoke pipeline](/colibri/colibri-core/pipelines/invoke-contract.md).