Why marketplaces are blocked by AI buying agents

Autonomous shopping agents with artificial intelligence are rapidly moving from novelty to reality, with both financial and legal implications.

AI-powered browsers like Perplexity’s Comet and OpenAI’s Atlas can now search, compare and initiate purchases with minimal human intervention.

This process, called agency commerce, ensures faster shopping for consumers and fewer clicks for merchants. It also challenges many of the conventions of e-commerce, including the role that marketplaces play in product discovery, transactions, and advertising.

Amazon and eBay responded. Both are set to restrict independent AI agents from completing purchases, citing security and user concerns. But in reality, the fight is almost certainly about control.

Amazon vs. confusion

In November 2025, Amazon sued Perplexity, alleging that the Comet web browser was impersonating people, accessing Amazon accounts, and placing orders in violation of Amazon’s terms of service and computer fraud laws.

According to Amazon, third-party bots must operate openly and only with the permission of the platform.

Perplexity countered that Comet was acting on behalf of a human, with credentials stored locally for security, and suggested Amazon’s action was an attempt to protect its ad-based business model and maintain control over shopping flows.

Perplexity essentially asks if the platform can say no if a human allows the AI ​​to shop.

eBay ban

Just this month, eBay updated its user agreement to ban buy-for-me agents and LLM-driven end-to-end payment flows without prior approval.

eBay positions the change as a safeguard against auction manipulation, fraud and erroneous orders. However, the company left room for “formally sanctioned” buying agents, opening the door for partnerships that eBay can control.

Market concerns

Taken together, eBay’s update and Amazon’s lawsuit suggest that the marketplace is trying to control agents’ business relationships.

It makes sense. Marketplaces exist to aggregate and centralize shopping. It’s the core service they provide and how they make money. So agent trading is a threat.

Advertising. For the Amazon marketplace in particular, and for other marketplaces in general, advertising revenue is probably the main concern.

Amazon generated $47 billion in “advertising services” revenue in the first nine months of last year, according to its third-quarter 2025 filing with the Securities and Exchange Commission.

A company is much more than just a product market. It’s also a publisher that offers sponsored listings, referral units, and paid placements—all deeply embedded in search results and category pages.

Autonomous agents bypass ads. Instead of scrolling through sponsored products and AI recommendations, the shopping agent jumps to an item and initiates checkout.

First party data. A related concern is shopper data.

E-commerce marketplaces monitor, track and use information about shopper behavior. They track what customers search for, what products they view, and what they leave. These signals feed ranking algorithms, recommendation systems and personalization models.

This data disappears when an external AI agent makes comparisons and decisions outside of the marketplace, which only sees the final purchase.

Transaction. In its case against Perplexity, Amazon did not dispute that the AI ​​agent completed the transaction through Amazon’s own checkout. However, AI-driven checkout raises at least two concerns.

First, the marketplace has no way to ensure that the transaction is correct. What if the AI ​​agent made a mistake? What if the price is wrong? Could these mistakes lead to customer service issues or even increased returns? Maybe.

Second, upselling becomes arguably impossible when a human shopper never sees it.

Compromise

However, developers of AI shopping agents disagree.

Agentic commerce startups argue that customers should be free to choose their preferred AI when interacting with services or websites. The argument is that an AI agent is more like a browser or facilitation tool than a competitor.

According to the developers, marketplaces that allow only a few AI partners lock out human shoppers, stifle innovation and encourage monopolies.

The upcoming compromise is likely to allow markets to approve access within reasonable limits.

So AI agents, perhaps even Perplexity’s Comet, end up accessing the marketplace through official APIs, subject to rate caps, identity verification, and possibly trade arrangements. Think affiliate programs for bots that pay for access.

For e-commerce SMEs, the agent-marketplace relationship will likely be the primary route to get products onto Perplexity, ChatGPT and similar platforms. It could be a key revenue stream.