In B2B ecommerce, one size never fits all. Every business develops unique workflows and processes organically over the years. These vary but include negotiated pricing, custom catalogs, bulk ordering, purchase approvals, and complex fulfillment requirements. 

An extensible eCommerce platform provides the flexibility to adapt and customize to specific business needs while keeping pace with evolving market demands.

We can modify a famous quote, usually attributed to General Robert H. Barrow: “Amateurs talk about tactics, but professionals study logistics.”

Tactics are important, but it's logistics that enable those tactics and keep an army agile and well-supplied. Long-term thinking and planning are required. It’s the difference between winning a single battle and winning a long, protracted war. 

So let’s modify this principle for B2B companies: 

Amateurs shop for features. Professionals architect for tomorrow. 

And it’s APIs and data structures that help professionals architect for that tomorrow.

Why API extensibility matters for B2B commerce

A primary driver for extensibility is integration. B2B commerce doesn't operate in isolation but exists within an ecosystem of enterprise software. An extensible API makes it possible to integrate third-party applications and backend systems quickly, connecting your eCommerce platform with ERPs, CRMs, inventory management systems, procurement platforms, and more.

Many out-of-the-box B2C platforms lack robust APIs for complex B2B data flows. They are left with hacks or workarounds. These lead to further jury-rigged solutions built on top of a house of cards, and one day you wake up unable to make a simple change without breaking your website. When the time comes for an upgrade or migration, the data is a mess. Think of a Frankenstein-like suite of Shopify apps or WooCommerce plugins that each reside in their own silos with different data models that can’t easily communicate with each other.

By contrast, a strong API allows sellers to build custom solutions for unique, complex business models that differ from one customer to the next. This might mean delivering account-specific pricing, integrating with a buyer's procurement system, or providing custom checkout workflows (like the auction system for Whisky Auctioneer).

When deciding on a platform, its API and underlying architecture should be a factor in your evaluation.

The three pillars of API extensibility

1. Rapid integration capabilities. Well-designed, extensible APIs allow rapid third-party integrations, which is particularly valuable in B2B scenarios involving complex supply chains or customer-specific requirements. A robust API turns an eCommerce platform into a set of building blocks that developers can recombine or extend. The Irish Times was able to use Drupal Commerce’s composability to support complex validation for delivery zones while integrating with eSuite, its subscription management system.
2. Custom feature development. Every business has at least one distinct requirement or innovative idea. An API allows the platform to be tailored accordingly. Instead of waiting for a vendor's roadmap, companies can rapidly build needed features by leveraging public APIs or extension frameworks. A company can adopt new technology without replatforming. Worthington Biochemical was able to automate its current fulfillment processes with Drupal Commerce, while still maintaining the relationships between sales staff and customers.
3. Scalability and future growth. An eCommerce platform must be able to grow as the company grows. New services to handle emerging needs. More traffic. Expansions to new locales and languages. RiffTrax, for example, launched a marketplace for its community on Drupal Commerce, the same platform that powers its digital sales. No new platform needed.

With AI, API extensibility matters more than ever

API extensibility is already important for B2B commerce, but we’re at an inflection point. The convergence of extensible APIs and AI-powered development hints at what might be possible in eCommerce, and as a result, what businesses should expect from their platforms.

AI-accelerated development

Generative AI coding assistants can produce integration code snippets, API calls, and even entire applications based on natural language prompts. If your eCommerce platform has a well-documented and accessible API, AI tools can help developers stitch together systems much more rapidly.

The better and more extensible the API, the more the AI can accomplish. Platforms with complete API coverage and clear documentation effectively enable AI copilots to become "integration developers" on demand. Businesses on platforms like this could have a huge advantage, both in total cost of ownership and in speed to market with new features.

Low-code/no-code tools

Less technical users or overburdened IT teams can set up integrations or develop new features by describing what they need. This capability puts businesses back in control of their own future.

OutSystems highlights how its AI-powered development environment allows enterprises to "extend legacy system capabilities without disrupting core operations" and use AI to "accelerate development while maintaining compatibility". The presence of extensible APIs under the hood is what makes this possible.

If your eCommerce platform's API is well-designed, it can more easily be packaged into a connector or used by an AI-driven orchestration tool.

A glimpse of the future

What happens when AI can generate what you need on demand? You don’t need to go searching through an app store. You don’t need to browse a module directory. You don’t need to perform a gap analysis to determine the level of effort. You don’t need to hire an agency to build a new feature. Need a new payment gateway integration? Need a new price comparison feature? Need a new type of promotion? Write a few prompts, and the feature is ready to test. Maintaining it is just as simple.

But this only works if the underlying platform has a robust, stable, well-documented API. If this future manifested tomorrow, would your business be ready to benefit?

Which eCommerce platforms are ready for the AI future?

When evaluating platforms for B2B commerce, API extensibility should be one of your main comparison criteria. It will determine if you’ll be able to develop certain functionality in the future and how well you can integrate your current systems and processes. And it exists on a spectrum. Many platforms might have the capability, but the cost and time to develop might be prohibitive, or the connections might not be performant.

Here's how the major platforms stack up.

Drupal Commerce - maximum API extensibility and coverage

For B2B organizations with complex, unique requirements, Drupal Commerce offers unmatched API extensibility.

• API architecture - Drupal has spent over a decade honing its data model and API to be service-based and API-first. It’s fully composable. You can expose new endpoints or modify existing ones to match your business logic. You can consume data from other APIs and integrate them seamlessly. You can pull out entire chunks and replace them with your own. Need to implement contract-based pricing that pulls from three different systems? Sure. Need to integrate with a legacy inventory system that uses SOAP? You can do that too.
• B2B integration capabilities - Build custom integrations with any backend system and couple them as tightly as you want. Whether you need to sync customer-specific price lists from an ERP, integrate with a buyer's punchout catalog system, or build custom approval workflows that span multiple systems, you have full access to extend virtually any aspect of the platform. Create your own data types that can store an unlimited number of fields. These data objects automatically become first-class citizens in your Drupal platform, with full API coverage.
• AI integration potential - The Drupal community has rapidly built AI integration modules, and because there are no proprietary constraints, you can integrate any AI service, sending data back and forth.

Bottom line: Drupal offers complete freedom to build exactly what you need. This level of API freedom is essential when your business processes don't fit a template. Best for organizations where B2B commerce is a core business function requiring deep integration with existing systems.

Shopify Plus - curated API ecosystem

Shopify Plus provides extensive APIs but within a managed framework designed for broad applicability rather than specific B2B requirements.

• API architecture - Shopify is ultimately a closed platform. Limitations quickly arise when your B2B requirements fall outside Shopify’s data model. You cannot freely create new data structures or fundamentally alter how orders, customers, or products work. For example, if your pricing model requires multiple layers of contract negotiations, customer hierarchies, and approval chains that don't map to Shopify's account structure, you'll struggle to implement it cleanly via the API.
• B2B integration capabilities - Shopify's REST and GraphQL APIs are robust, and their Storefront API allows custom front-ends while Admin APIs let developers extend business logic. For standard B2B integrations—connecting to common ERPs like NetSuite, syncing with popular CRMs, or integrating shipping providers—there's likely an app. However, you won’t own the roadmap of the suite of apps you decide to use. Anything truly unique will require extensive custom development, or you’ll have to wait an unknown amount of time.
• AI integration potential - Shopify has built-in AI features, but integrating your own custom AI logic for B2B-specific needs requires working within API constraints. You can call external services, but you're limited in how you can store and act on the results within Shopify's data model. AI-powered development will be able to create Shopify apps for you, but you will still hit these same constraints.

Bottom line: Suitable for straightforward B2B scenarios where your processes can adapt to Shopify's model. Challenging when you need deep customization of business logic or complex multi-system integrations that require custom data structures.

BigCommerce - open SaaS for B2B

BigCommerce bridges managed infrastructure with serious API openness, particularly valuable for B2B.

• API architecture - Unlike pure SaaS platforms, BigCommerce encourages API-first implementations. You can pull catalog and customer data into external systems for processing (like running complex pricing calculations in your ERP), then push results back. Their webhook system is robust for real-time integrations. For example, when an order is placed, you can trigger processes in multiple backend systems. It explicitly supports composable approaches, so you can use BigCommerce as the commerce engine while integrating with best-of-breed solutions for content, personalization, or complex pricing
• B2B integration capabilities - BigCommerce provides REST and GraphQL APIs with specific attention to B2B needs. Their APIs expose customer groups, account hierarchies, and quote management, all of which are critical B2B entities.
• AI integration potential - BigCommerce’s open API means merchants can connect custom AI solutions, exporting data to machine learning services and importing results back.

Bottom line: A strong middle ground for organizations that want SaaS reliability with significant API flexibility for custom integrations. You can handle some complex B2B scenarios, though you still can't modify core platform logic.

WooCommerce - plugin-driven extensibility

WooCommerce leverages WordPress's plugin architecture for extensibility, with all the strengths and weaknesses that come with it.

• API architecture - The challenge for B2B is that WooCommerce's data model relies on WordPress's posts and meta tables, which can make deep customization or heavy integration cumbersome for large B2B applications. Complex B2B entities and logic, like customer hierarchies, contract pricing, or approval workflows, aren't native concepts. They must be built on top of the existing structure, often requiring multiple plugins to work together (not always guaranteed, even from the same company/developer), on top of an architecture that was never intended to hold that much weight.
• B2B integration capabilities - WooCommerce can leverage the WordPress REST API for integrations, and many SaaS services provide WordPress plugins for common connections. The platform's open-source nature means developers can write custom plugins to extend any aspect of the system. And while the WordPress plugin ecosystem is vast, quality varies significantly, and ensuring multiple plugins work together reliably for mission-critical B2B integrations requires careful vetting and testing.
• AI integration potential - The WordPress ecosystem has quickly produced numerous AI plugins for content generation, chatbots, and basic personalization. You can also integrate external AI tools and services. However, the plugin ecosystem has no real consistency, so exposing all of your data in the way you need it could be a chore and introduce fragility into your platform.

Bottom line: WooCommerce can work well for straightforward B2B scenarios or content-driven commerce where WordPress's strengths (and simplicity) can be leveraged. For enterprise B2B with complex integrations, the platform's architecture can become strained, and the plugin-based approach may lack the consistency and performance needed for stable, long-term integrations.

API extensibility can be a competitive differentiator

The convergence of API extensibility and AI readiness opens up a lot of opportunities for those with the infrastructure to embrace it. Organizations that can rapidly integrate new capabilities, customize workflows to their exact needs, and leverage AI to automate complex processes will outpace those constrained by rigid, poorly documented, or unstable platforms.

As you evaluate eCommerce platforms for your B2B organization, ask:

• Can this platform's API support AI-generated integrations?
• Will this API remain stable as we scale?
• Does this platform expose the functionality we need via API?
• Can we customize this platform to match our unique workflows?
• Is the documentation machine-readable and comprehensive?

The answers to these questions will determine not just what your eCommerce platform can do today, but what it will enable tomorrow. API extensibility might be the difference between leading your market and struggling to keep up.