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Peddler is a Ruby interface to the Amazon MWS API, a collection of web services that help Amazon sellers programmatically exchange data on their listings, orders, payments, reports, and more.

To use Amazon MWS, you must have an eligible seller account and register for MWS. This applies to developers as well.

Some MWS API sections may require additional authorisation from Amazon.



Require the library.

require "peddler"

Create a client. Peddler provides one for each MWS API under an eponymous namespace.

client =

# or the shorthand
client = MWS.orders

Each client requires valid MWS credentials. Set these globally in the shell.


You can now instantiate a client. The client will pick up credentials automatically from the environment.

client = MWS.orders

If you are creating a client for another seller, pass the latter's Merchant (Seller) ID and Marketplace ID along with the MWSAuthToken they obtained for you.

client = MWS.orders(
  primary_marketplace_id: "Seller's Marketplace ID",
  merchant_id: "Seller's Merchant or Seller ID",
  auth_token: "Seller's MWS Authorisation Token"

Finally, if you do not want to use environment variables at all, you can set all credentials when or after creating the client.

client = MWS.orders(
  primary_marketplace_id: "Your Marketplace ID",
  merchant_id: "Your Merchant or Seller ID",
  aws_access_key_id: "Your AWS Access Key ID",
  aws_secret_access_key: "Your AWS Secret Access Key",

client.primary_marketplace_id = "Another Marketplace ID"

Once you have a client with valid credentials, you should be able to make requests to the API. Clients map operation names in a flat structure. Methods have positional arguments for required input and keyword arguments for optional parameters. Both method and argument names are underscored but otherwise identical to the names of the corresponding operations and parameters documented in the API.


Peddler wraps successful responses in a parser that handles both XML documents and flat files:

parser = client.get_service_status
parser.parse # will return a Hash object
parser.dig('Status') # delegates to Hash#dig if available

You can swap the default parser with a purpose-built abstraction.

MWS::Orders::Client.parser = MyParser

For a sample implementation, see my MWS Orders library.


Amazon limits the number of requests you can submit to a given operation in a given amount of time.

Peddler exposes header values showing the hourly quota of the current operation:

res = client.some_method
puts res.quota
#<struct Quota max=200, remaining=150, resets_on=2017-01-01 00:12:00 UTC>

Read Amazon's tips on how to avoid throttling.


If you are having trouble with a request, read the Amazon documentation. Also, Peddler's source links individual operations to their corresponding entries in the Amazon docs.

Note that some optional keywords have default values.

To introspect requests, set the EXCON_DEBUG environment variable to 1 or similar truthy value. Peddler will then log request and response internals to stdout.


Handle network errors caused by throttling or other transient issues by defining an error handler.

MWS::Orders::Client.on_error do |e|
  if e.response.status == 503
    logger.warn e.response.message

Alternatively, rescue.

rescue Excon::Error::ServiceUnavailable => e
  logger.warn e.response.message

Peddler has an optional new error handler that raises more descriptive errors: for instance, Peddler::Errors::RequestThrottled instead of Excon::Error::ServiceUnavailable. This error handler will become the default in the next major version.

To start using this now:

require 'peddler/errors'

The APIs


The MWS Feeds API lets you upload inventory and order data to Amazon. You can also use this API to get information about the processing of feeds.


The MWS Finances API enables you to obtain financial information relevant to your business with Amazon. You can obtain financial events for a given order, financial event group, or date range without having to wait until a statement period closes. You can also obtain financial event groups for a given date range.

Fulfillment Inbound Shipment

With the MWS Fulfillment Inbound Shipment API, you can create and update inbound shipments of inventory in the Amazon Fulfillment Network. You can also also request lists of inbound shipments or inbound shipment items based on criteria that you specify.

Fulfillment Inventory

The MWS Fulfillment Inventory API can help you stay up-to-date on the availability of your inventory in the Amazon Fulfillment Network. The Fulfillment Inventory API reports real-time availability information for your Amazon Fulfillment Network inventory regardless of whether you are selling your inventory on Amazon's retail web site or through other retail channels.

Fulfillment Outbound Shipment

The MWS Fulfillment Outbound Shipment API enables you to fulfill orders placed through channels other than Amazon's retail web site, using your inventory in the Amazon Fulfillment Network. You can request previews of potential fulfillment orders that return estimated shipping fees and shipping dates based on shipping speed. You can get detailed item-level, shipment-level, and order-level information for any existing fulfillment order that you specify. You can also request lists of existing fulfillment orders based on when they were fulfilled and by the fulfillment method associated with them.

Support for creating and cancelling fulfillment orders has been implemented, but the rest of the API is not supported yet.

Merchant Fulfillment

The Merchant Fulfillment API provides programmatic access to Amazon’s fulfillment shipping services for sellers, including competitive rates with Amazon-partnered carriers. Sellers can find out what shipping services are available by submitting information about a proposed fulfillment shipment, such as package size and weight; shipment origin and destination; and delivery date requirements. Sellers can choose from the shipping service options returned by Amazon, and then receive shipping labels for fulfilling their orders.

Off Amazon Payments

The MWS Off-Amazon Payments API helps you to process payments for purchases made by buyers on your website using the Login and Pay with Amazon service. This API enables you to programmatically retrieve shipping and payment information provided by the buyer from their Amazon account. It allows you to authorize, capture, and refund payments, enabling a variety of payments scenarios.

You can switch the client to the sandbox environment:

client = MWS.off_amazon_payments.sandbox


With the MWS Orders API, you can list orders created or updated during a time frame you specify or retrieve information about specific orders.


The MWS Products API helps you get information to match your products to existing product listings on Amazon Marketplace websites and to make sourcing and pricing decisions for listing those products on Amazon Marketplace websites.


The Recommendations API enables you to programmatically retrieve Amazon Selling Coach recommendations by recommendation category. A recommendation is an actionable, timely, and personalized opportunity to increase your sales and performance.


The Reports API lets you request reports about your inventory and orders.


The Sellers API lets sellers retrieve information about their seller account, such as the marketplaces they participate in.


The Amazon MWS Subscriptions API section enables you to subscribe to receive notifications that are relevant to your business with Amazon. With the operations in the Subscriptions API section, you can register to receive important information from Amazon without having to poll the Amazon MWS service. Instead, the information is sent directly to you when an event occurs to which you are subscribed.