adagents.json vs ads.txt and schain: Four Files, Two Supply-Chain Questions
In early October 2026, IAB Tech Lab's programmatic supply-chain leadership pushed back on the idea that adagents.json should replace ads.txt , sellers.json , and the OpenRTB SupplyChain object. The argument, echoed in trade coverage of Hillary Slattery's rebuttal, is that the IAB files already answer who may sell inventory and how a bid request moved. AgenticAdvertising.org's answer is different:…
In early October 2026, the IAB Tech Lab's supply-chain leadership questioned whether adagents.json could replace ads.txt, sellers.json, and the OpenRTB SupplyChain object. The IAB files already cover who may sell inventory and how a bid request moved, while AgenticAdvertising.org focuses on authorized sales agents for agentic negotiation.
Both are distinct questions, and the auction payload only embeds one of them. AdCP, Prebid Sales Agent, and buyer-side agents need both sets of mental models as they cannot rely on just one file. adagents.json lives at /.well-known/adagents.json and lists authorized agents with agent URLs, property or placement scope, delegation type, exclusivity, and time bounds.
It is tied to the Ad Context Protocol family. The buyer agent should fetch this file before treating an agent as allowed to sell a slice of inventory. adagents.json does not replace ads.txt, sellers.json, or schain; they each serve different purposes in authorizing inventory sales and tracking the impression journey.
Written by urgent.news from Dev.to's reporting — not their text. Machine-written — may contain errors; check the original before relying on it.
