> For the complete documentation index, see [llms.txt](https://docs.somnia.network/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.somnia.network/agents/base-agents/json-api-request.md).

# JSON API Request

Fetches JSON data from any public API endpoint and extracts specific values using a selector path. This agent is the fundamental building block for creating on-chain oracles.

## Methods

| Function           | Inputs                  | Output     | Use Case                     |
| ------------------ | ----------------------- | ---------- | ---------------------------- |
| `fetchString`      | url, selector           | string     | Text values, names           |
| `fetchUint`        | url, selector, decimals | uint256    | Prices, positive numbers     |
| `fetchInt`         | url, selector, decimals | int256     | Temperatures, signed numbers |
| `fetchBool`        | url, selector           | bool       | Flags, status checks         |
| `fetchStringArray` | url, selector           | string\[]  | Lists of names/IDs           |
| `fetchUintArray`   | url, selector, decimals | uint256\[] | Price lists, numeric arrays  |

## Parameters

| Input      | Type   | Description                                                                              |
| ---------- | ------ | ---------------------------------------------------------------------------------------- |
| `url`      | string | The URL of the JSON API endpoint to fetch                                                |
| `selector` | string | A dot-notation path to extract from the response (e.g., `data.price` or `items[0].name`) |
| `decimals` | uint8  | Number of decimal places to scale the value by (multiplies by 10^decimals)               |

### Decimal Scaling

The `decimals` parameter is used by `fetchUint`, `fetchInt`, and `fetchUintArray` to convert floating-point values from APIs into blockchain-compatible integers. The value is multiplied by 10^decimals.

For example, with `decimals=8`:

* `42000.50` becomes `4200050000000`
* `0.00001234` becomes `1234`

This follows the standard pattern for handling decimals in smart contracts (e.g., ERC-20 tokens typically use 18 decimals).

## Method Signatures

```solidity
function fetchString(string url, string selector) returns (string)
function fetchUint(string url, string selector, uint8 decimals) returns (uint256)
function fetchInt(string url, string selector, uint8 decimals) returns (int256)
function fetchBool(string url, string selector) returns (bool)
function fetchStringArray(string url, string selector) returns (string[])
function fetchUintArray(string url, string selector, uint8 decimals) returns (uint256[])
```

## Example Use Cases

* Fetching cryptocurrency prices from CoinGecko or similar APIs
* Retrieving weather data for parametric insurance contracts
* Pulling sports scores for prediction markets
* Accessing any REST API that returns JSON

## Usage Examples

### Fetch a Price as uint256

```javascript
import { encodeFunctionData } from 'viem';

const abi = [{
  type: 'function',
  name: 'fetchUint',
  inputs: [
    { name: 'url', type: 'string' },
    { name: 'selector', type: 'string' },
    { name: 'decimals', type: 'uint8' }
  ],
  outputs: [{ name: 'result', type: 'uint256' }]
}];

// Fetch Bitcoin price with 8 decimal places
const calldata = encodeFunctionData({
  abi,
  functionName: 'fetchUint',
  args: [
    'https://api.coingecko.com/api/v3/simple/price?ids=bitcoin&vs_currencies=usd',
    'bitcoin.usd',
    8
  ]
});
```

### Fetch a String Value

```javascript
const abi = [{
  type: 'function',
  name: 'fetchString',
  inputs: [
    { name: 'url', type: 'string' },
    { name: 'selector', type: 'string' }
  ],
  outputs: [{ name: 'result', type: 'string' }]
}];

// Fetch a token symbol
const calldata = encodeFunctionData({
  abi,
  functionName: 'fetchString',
  args: [
    'https://api.example.com/token/info',
    'data.symbol'
  ]
});
```

### Fetch a Boolean Value

```javascript
const abi = [{
  type: 'function',
  name: 'fetchBool',
  inputs: [
    { name: 'url', type: 'string' },
    { name: 'selector', type: 'string' }
  ],
  outputs: [{ name: 'result', type: 'bool' }]
}];

// Check if a market is open
const calldata = encodeFunctionData({
  abi,
  functionName: 'fetchBool',
  args: [
    'https://api.example.com/market/status',
    'isOpen'
  ]
});
```


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://docs.somnia.network/agents/base-agents/json-api-request.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.