How to Access the Amazon Seller API (Step-by-Step Guide)

Whether you’re an individual seller or a tech-savvy eCommerce brand, integrating with the Amazon Seller API – officially known as the Selling Partner API (SP-API) – can completely transform your business. It allows you to automate product listings, sync inventory across platforms, monitor ads, pull reports, and much more.

What is the Amazon Seller API?

The Amazon Seller API (SP-API) is Amazon’s official programmatic interface for third-party developers and sellers. It replaces the legacy MWS (Marketplace Web Service) and supports a more modern, secure, and expansive ecosystem.

With SP-API, you can connect your app or software to:

• Upload or update product listings

• Retrieve order details

• Manage inventory across FBA and FBM

• Pull advertising and performance reports

• Automate pricing and fulfillment

Why Sellers and Developers Should Care

If you’re still manually uploading inventory or downloading reports from Seller Central, you’re wasting valuable time.

Integrating with the Amazon SP-API enables:

✅ Real-time automation
✅ Cross-channel synchronization (eBay, Walmart, Shopify, etc.)
✅ Smarter repricing and inventory control
✅ Actionable insights from custom reports
✅ Scalable workflows without human bottlenecks

RockitSeller leverages the SP-API under the hood to power tools like Sellwise, Pricewise, and Adstein, giving sellers a no-code way to harness the power of automation.

Step-by-Step: How to Access the SP-API

Step 1: Register as a Developer

Log in to Seller Central and navigate to Developer Central. Register your developer profile and create your developer credentials.

If you’re building internal tools, you’ll register under your own seller account. For third-party apps, apply for public access.

Step 2: Create and Configure a Security Profile

Go to Amazon’s App Console and create a new security profile:

• Name your app

• Add privacy policy and terms URLs

• Generate a client ID and client secret

You’ll need these to request OAuth tokens.

Step 3: Request API Role Access

Depending on what you’re trying to access (orders, inventory, ads, reports), you must request access to specific roles/scopes.

Use RockitSeller’s integration guide to know which scopes are required for each module.

Step 4: Set Up IAM and Role Assumption

Amazon requires all API calls to use IAM role-based authentication.

• Set up an IAM user in AWS

• Attach the AmazonSPAPIAccess policy

• Create a role that trusts sellingpartnerapi.amazon.com

• Save your role ARN and external ID

This is one of the trickiest parts – RockitSeller’s walkthrough has a preconfigured policy JSON you can copy.

Step 5: Exchange Tokens and Make API Calls

Once everything is configured:

• Exchange your client credentials for an LWA access token

• Assume the IAM role using AWS STS

• Use the LWA token + role credentials to call the SP-API

Use RockitSeller’s Postman collection or prebuilt Lambda templates to test your first calls.

Key Endpoints You Can Use

Here are some high-impact SP-API endpoints you can integrate with:

SP-API Use Cases (What You Can Build)

Here are real-world examples of what sellers and developers build using the Amazon Seller API:

• A Chrome extension to monitor BSR, price, and seller count

• A pricing bot that auto-adjusts based on competitor changes

• An inventory sync tool between Amazon and Walmart

• An order routing system for multi-warehouse fulfillment

• A VA dashboard to monitor account health and trends

• Scheduled downloads of weekly business reports to Google Sheets

RockitSeller combines all of these through its no-code platform so you don’t have to start from scratch.

What If You’re Not a Developer?

Even if you’re not a coder, you can still benefit from SP-API power via RockitSeller:

• No-code automations built on SP-API (like in Automation Vault)

• Sellwise for listing and inventory management

• Adstein for optimizing Amazon PPC using API data

• Done-for-you integrations if you want something custom

Common Errors (and Fixes)

• 403 Unauthorized: Usually a misconfigured IAM role trust relationship

• 400 Bad Request: Check required parameters (like marketplaceIds)

• 401 Token Expired: Refresh your LWA token every 1 hour

• Quota errors: Make sure you haven’t exceeded Amazon’s rate limits

Conclusion

Accessing the Amazon Seller API opens the door to total business automation. Whether you want to sync listings, automate pricing, analyze ads, or pull detailed reporting, SP-API is the backbone that powers the most sophisticated seller tools.