Application Programming Interface

Key points

• API, short for application programming interface, is the set of functions that lets a system talk to the data and resources of another service.
• In the crypto market, APIs from exchanges and infrastructure providers allow price queries, order submission, and asset transfers without manual intervention.
• Access is controlled through API keys, which should carry minimal permissions and withdrawal restrictions to reduce the damage in case of a leak.

What is an API?

An API is a collection of functions and procedures that lets a program interact with the data of an application or service, such as an exchange, and execute its functionality automatically. Instead of operating through a screen, one system connects to another through standardized calls, receiving structured responses.

How it works

An API defines a contract: which requests are accepted, with which parameters, and in what format the responses come back. A program sends a request, the service processes it and returns the result, typically in JSON format. This standard allows integrating systems written in different languages, as long as both respect the contract.

In the crypto market, there are two common patterns. REST APIs handle one-off queries, such as fetching an asset's price or an account's balance. WebSocket connections deliver continuous data streams, useful for tracking the order book in real time. Node providers expose APIs for reading from and writing directly to the blockchain.

Access is usually authenticated through API keys, a pair of credentials that identifies who is making the call. Good practices include granting only the necessary permissions, restricting by IP address, and disabling withdrawals when the key is only meant for reading data or submitting orders.

Many services apply request limits, known as rate limits, which define how many calls a client can make per time interval. Respecting these limits and handling errors predictably is part of a stable integration, especially in systems that depend on real-time data.

Why it matters

For companies, the API is what allows crypto to connect to internal systems: reconciliation, invoice issuance, and automatic settlement. A PIX/BaaS provider, for example, exposes APIs to create charges and reconcile incoming payments, the same way an exchange exposes trading APIs. Integration via API is what makes operations at scale viable without repeated manual work.

Risks and limitations

Leaked API keys are equivalent to direct account access within the granted permissions. Phishing attacks and misconfigured code repositories are frequent causes of exposure. Limiting permissions, rotating keys, and respecting request limits are basic security and stability measures.