Prerequisites

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Before you can start coding your first client application, there are a few things you need to do, if you haven't done them already.

Get a Google Account

You need a Google Account in order to create a project in the Google API Console. If you already have an account, then you're all set.

You may also want a separate Google Account for testing purposes.

Create a project for your client

Before you can send requests to Google Knowledge Graph Search API, you need to tell Google about your client and activate access to the API. You do this by using the Google API Console to create a project, which is a named collection of settings and API access information, and register your application.

To get started using Google Knowledge Graph Search API, you need to first use the setup tool, which guides you through creating a project in the Google API Console, enabling the API, and creating credentials.

If you haven't done so already, create your application's API key by clicking Create credentials > API key. Next, look for your API key in the API keys section.

Learn REST basics

There are two ways to invoke the API:

If you decide not to use client libraries, you'll need to understand the basics of REST.

REST is a style of software architecture that provides a convenient and consistent approach to requesting and modifying data.

The term REST is short for "Representational State Transfer." In the context of Google APIs, it refers to using HTTP verbs to retrieve and modify representations of data stored by Google.

In a RESTful system, resources are stored in a data store; a client sends a request that the server perform a particular action (such as creating, retrieving, updating, or deleting a resource), and the server performs the action and sends a response, often in the form of a representation of the specified resource.

In Google's RESTful APIs, the client specifies an action using an HTTP verb such as POST, GET, PUT, or DELETE. It specifies a resource by a globally-unique URI of the following form:

https://www.googleapis.com/apiName/apiVersion/resourcePath?parameters

Because all API resources have unique HTTP-accessible URIs, REST enables data caching and is optimized to work with the web's distributed infrastructure.

You may find the method definitions in the HTTP 1.1 standards documentation useful; they include specifications for GET, POST, PUT, and DELETE.

REST in the Google Knowledge Graph Search API

The Google Knowledge Graph Search API operations map directly to REST HTTP verbs.

The specific formats for Google Knowledge Graph Search API URIs are:

https://kgsearch.googleapis.com/v1/entities:search?query=your_query&parameters

The full set of URIs used for each supported operation in the API is summarized in the Google Knowledge Graph Search API Reference document.

Learn JSON basics

The Google Knowledge Graph Search API returns data in JSON format.

JSON (JavaScript Object Notation) is a common, language-independent data format that provides a simple text representation of arbitrary data structures. For more information, see json.org.