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GlossaryProductsNew to AI

APIs

Also written: API, OpenAPI 3.x, OpenAPI Specification, Agents API, API spec, API specification, REST APIs, REST API

Tools that let different software programs talk to each other and share information or functions.

In plain terms

APIs, or Application Programming Interfaces, are like a menu in a restaurant. The menu lists what you can order, and the waiter (the API) takes your order to the kitchen (another software program) and brings back your food (the result). They allow different software to work together without needing to know how the other program works internally.

For example, when you use a weather app on your phone, it doesn't have its own weather sensors. Instead, it uses an API to ask a weather service's computer for the current temperature and forecast. The weather service's computer sends the information back through the API, and your app displays it.

The expert version

Application Programming Interfaces (APIs) define a contract of calls or requests that can be made to a software component, specifying how to format them, what data to include, and what to expect in return. They abstract complex underlying logic, enabling interoperability between disparate systems. This allows developers to integrate functionalities, such as AI model access or data retrieval, into their own applications without needing to build those capabilities from scratch.

Why it matters now

Frontier AI labs are increasingly exposing their models and capabilities through APIs. This allows developers to integrate AI into their own applications and workflows, as seen with Copilot's API support for code reviews and Gemini's ability to expose REST APIs to AI agents. OpenAI also highlights its API platform, indicating its importance for broader AI adoption and development.

Where it shows up 30 items, newest first
How each company uses it
Google Gemini
Google Gemini is enabling developers to turn their REST APIs into tools for AI agents and is integrating directly with hardware sensors.
Meta Meta AI
Meta is updating its AI developer tools, making advanced AI accessible for building new applications, likely through APIs.
Microsoft Copilot
Microsoft Copilot is adding API support to automate code reviews within existing workflows.
OpenAI ChatGPT
OpenAI is emphasizing its API platform and providing resources like the Cookbook to help developers understand and use its agent capabilities.
Related terms

SDKsWebhooksAI AgentsCloud ComputingMicroservicesLLM APIs

Often confused with
SDKs
Software Development Kits are collections of tools, libraries, and documen
Webhooks
Webhooks are automated messages sent from apps when something happens,
Cloud Computing
Cloud computing provides on-demand computing resources over the
Libraries
Libraries are collections of pre-written code that developers can use
Origin

The concept of APIs emerged with the development of operating systems and software libraries in the mid-20th century, allowing different programs to interface with each other. Early examples include the interfaces for operating systems like Unix. Source ↗

Try this about 5 minutes

Go to the website of a service you use, like a social media platform or a cloud storage provider. Look for a 'Developers' or 'API' section. You can often find documentation explaining how to use their API to interact with their service programmatically, for example, to post an update or retrieve a file.

Try it: Playbook entries that use thisPlaybook →

The Playbook: reusable how-tos, prompts, configs and tips pulled out of the news.

Questions people ask

What is an API key?
An API key is a unique identifier used to authenticate a user or application when making requests to an API, often used for tracking usage and security.
Are APIs free to use?
Some APIs are free, while others have costs associated with them, often based on usage volume or the features provided. Frontier AI APIs typically have usage-based pricing.
How do I choose the right API?
Choose an API that provides the specific functionality you need, has clear documentation, a reliable service level agreement, and a pricing model that fits your budget and usage.

First seen on Subvolts Oct 31, 2024. Updated Oct 16, 2026. Written by an AI model from the items above and reviewed against them weekly; report an error.