Mock sample for your project: LetMC Api V2, Free (Tier 1) API

Send an SMS with verification code and a custom message for authentication purpose. It helps merchants to minimize chargebacks and fraud for various kinds of payment method, such as credit card, paypal, cod and so on. Please visit https://www.fraudlabspro.com to learn more.

The Account API gives sellers the ability to configure their eBay seller accounts, including the seller's policies (the Fulfillment Policy, Payment Policy, and Return Policy), opt in and out of eBay seller programs, configure sales tax tables, and get account information. For details on the availability of the methods in this API, see Account API requirements and restrictions.

The Feed API lets sellers upload input files, download reports and files including their status, filter reports using URI parameters, and retrieve customer service metrics task details.

Documentation of the Billbee REST API to connect a Billbee account to external aplications.
Endpoint
The Billbee API endpoint base url is https://app.billbee.io/api/v1
Activation
You have to enable the API in the settings of your Billbee account. In addition you need a Billbee API Key identifying the application you develop. To get an API key, send a mail to [email protected] and send us a short note about what you are building.
Authorization & security
Because you can access private data with the Billbee API, every request has to be sent over https and must
Contain a valid API Key identifying the application/developer. It has to be sent as the HTTP header X-Billbee-Api-Key
Contain a valid user login with billbee username and api password in form of a basic auth HTTP header
Throttling
Each endpoint has a throttle of max 2 requests per second per combination of API Key and Billbee user.
When you exceed these 2 calls, the API will return a HTTP 429 status code

Please make sure you use the correct version of the APIs for your use case. To find out the appropriate version, go to the API Docs drop down on the menu.

Use the Fulfillment API to complete the process of packaging, addressing, handling, and shipping each order on behalf of the seller, in accordance with the payment method and timing specified at checkout.

https://www.beanstream.com/api/v1

reverb

Maintaining up-to-date inventory for your items on Walmart.com ensures a great experience for your customers and greater sales opportunities for you.

Just Eat API
Just Eat offers services for our various business partners and our consumer applications.
How you interact with the API depends on the services you wish to interact with.
Security
HTTPS
All api calls and callbacks require HTTPS. Your service will need a valid SSL certificate and be accessible via the standard SSL port (port 443).
Making an API request
Some API calls require an API key, to authenticate the partner calling the API.

The Catalog API allows users to search for and locate an eBay catalog product that is a direct match for the product that they wish to sell. Listing against an eBay catalog product helps insure that all listings (based off of that catalog product) have complete and accurate information. In addition to helping to create high-quality listings, another benefit to the seller of using catalog information to create listings is that much of the details of the listing will be prefilled, including the listing title, the listing description, the item specifics, and a stock image for the product (if available). Sellers will not have to enter item specifics themselves, and the overall listing process is a lot faster and easier.