> For the complete documentation index, see [llms.txt](https://docs.frequencychain.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.frequencychain.org/15.-apis-and-sdk-integration.md).

# 15. APIs and SDK Integration

The FreCx network exposes its functionality to developers through a set of RPC interfaces, programmatic APIs, and SDK-compatible patterns, enabling applications to interact with the blockchain in a structured and scalable manner. These interfaces form the primary access layer through which developers can build applications, automate workflows, and integrate external systems with FreCx.

Unlike traditional APIs in centralized systems, blockchain interaction is inherently stateful and transaction-driven. Every operation—whether reading data or modifying state—must be routed through a node using defined protocols. FreCx provides these capabilities through standard JSON-RPC endpoints, along with compatibility for widely used development libraries such as ethers.js and web3.js.

This section explains how developers can interact with FreCx programmatically, construct application-level integrations, and build reusable SDK layers.

**RPC Interface and Network Communication**

At the core of FreCx integration lies the RPC interface, which allows applications to communicate directly with the blockchain network.

An RPC endpoint acts as a gateway to a FreCx node. Through this interface, developers can query blockchain state, retrieve account balances, read smart contract data and submit transactions.

FreCx provides publicly accessible RPC endpoints:

* Mainnet: [<sup>https://rpc.frequencychain.org</sup>](https://rpc.frequencychain.org)
* Testnet: [<sup>https://testrpc.frequencychain.org</sup>](https://testrpc.frequencychain.org)

To interact with these endpoints, developers send JSON-RPC requests over HTTP. Each request specifies a method, parameters, and an identifier.


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