overview page

docs/docs/overview.mdx

@@ -6,3 +6,51 @@ title: "Overview"
 # Overview
 
 Postcodes.io is a free postcode lookup API and geocoder for the UK
+
+## Endpoint
+
+All services can be accessed from the following HTTP[S] endpoint
+
+```javascript
+https://api.postcodes.io
+```
+
+The API accepts GET and POST requests. POST methods use content type `application/json`
+
+## Data Extraction
+
+The Postcodes.io application and database are packaged as Docker images for rapid local deployment and data extraction.
+
+To perform one-time data extraction tasks using SQL, see our [local data extraction guide](https://ideal-postcodes.co.uk/guides/postcodes-io-database).
+
+## Responses
+
+JSON(P) only. CORS is enabled.
+
+Each response comes with an appropriate HTTP Status code (except for JSONP requests). These include 200 for success, 400 for a bad request, 404 for not found and 500 for server error. The HTTP Status code is also included in the response body.
+
+## Authentication
+
+Postcodes.io does not require any authentication.
+
+## Error Handling
+
+To check for errors, examine the HTTP response code. 200 response indicates success while any other code will provide important information about why an error occured.
+
+Alternatively, you can examine status code in the 'status' property in the result body.
+
+All JSONP requests return 200 responses because of silent errors. When using JSONP, be sure to use the latter method to check for errors.
+
+## JSONP
+
+JSONP requests are supported. Simply appended the URI with a callback name. e.g.
+
+```javascript
+https://api.postcodes.io/postcodes/GU50BD?callback=foo
+```
+
+## Versioning
+
+The API currently does not use any form of versioning. Any changes to the API will be backwards-compatible, this includes: adding new properties to responses, adding new endpoints, adding new optional request parameters and changing the order of properties.
+
+If we make backwards-incompatible changes in the future, this will be released under a versioned endpoint.