Requests to the Bing Autosuggest API must use the HTTPS protocol.
We recommend that all requests originate from a server. Distributing the key as part of a client application provides more opportunity malicious third-party access. Additionally, making calls from a server provides a single upgrade point for future updates.
The request must specify the q query parameter, which contains the user's partial search term. Although it's optional, the request should also specify the mkt query parameter, which identifies the market where you want the results to come from. For a list of optional query parameters, see Query Parameters. All query parameter values must be URL encoded.
The request must specify the Ocp-Apim-Subscription-Key header. Although optional, you are encouraged to also specify the following headers:
User-Agent
X-MSEdge-ClientID
X-Search-ClientIP
X-Search-Location
The client IP and location headers are important for returning location aware content.
Source: Azure Documentation