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Model Context Protocol
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Concept

Model Context Protocol

An open standard enabling buyer and seller AI agents to exchange data and instructions without bespoke integration per pairing; developed by Anthropic.

Last refreshed: 28 June 2026 · Appears in 1 active topic

Key Question

Will MCP become the internet protocol of advertising, or will holding companies fragment into competing standards?

Timeline for Model Context Protocol

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Background

The Model Context Protocol (MCP) emerged as the de facto interoperability standard for agentic media buying on 18 June 2026 at Cannes Lions, when both WPP's Buyer Agent and Horizon Media's HorizonOS Blu were built on it, together committing roughly $17bn in annual media spend to a single protocol in one day.

MCP is an open standard, originally developed by Anthropic, that lets AI agents exchange data and instructions with external tools and services without bespoke integration per pairing. In media buying, it lets a Buyer Agent at an agency discover available inventory and request it from a seller agent at a broadcaster or platform through a common interface, eliminating the need for one-to-one API agreements between each buyer-seller pair.

The simultaneous adoption by WPP and Horizon at scale is the first cross-industry confirmation that MCP can serve as a standard commercial protocol in a multi-billion-dollar market outside software development tooling, and positions it as the likely foundation layer for the broader programmatic industry's shift to agent-to-agent trading.

Common Questions
What is the Model Context Protocol and why does it matter for advertising?
MCP is an open standard that lets AI agents exchange data and instructions without bespoke integration per pairing. In advertising, it allows a Buyer Agent at an agency to query and purchase inventory from a seller agent at a broadcaster through a common interface. WPP and Horizon Media both adopted it for agentic buying at Cannes Lions in June 2026.Source: event
Who created the Model Context Protocol?
MCP was originally developed by Anthropic as an open standard. It is now governed and adopted broadly across the AI industry, including by WPP and Horizon Media for media buying.
How much advertising spend runs through MCP?
As of 18 June 2026, WPP Media and Horizon Media together committed roughly $17bn in annual media spend to agentic buying on the Model Context Protocol at Cannes Lions.Source: WPP / Horizon Media
Source Material
Model Context Protocol

Written with AI from Lowdown's published reporting. Not individually reviewed by an editor. Updated 28 June 2026. Editorial standards.