> ## Documentation Index > Fetch the complete documentation index at: https://docs.interchange.io/llms.txt > Use this file to discover all available pages before exploring further. # One agent. Every seller. Every channel. > A technical introduction to building buyer agents on the Scope3 Interchange — for the engineers wiring the next twenty years of media buying. > Coming from the [Interchange overview](/v2/introduction)? This is the buyer-side deep dive — what you integrate, in the order you'll integrate it. First call in five minutes — sandbox advertiser, MCP connector, REST curl. The single URL your agent reads at startup to learn the entire API. OAuth into Claude or ChatGPT and drive the Interchange from any agent. ## You've integrated this market before. If you've shipped media-buying software in the last decade, you've written the same code five times. One adapter for each DSP. A separate SDK for CTV. Another for retail media. A scraper for the platform that still doesn't have an API. Every channel speaks a different language, and your integration backlog grows linearly with the market. That's not a protocol problem. That's the absence of one. ## The shift. Programmatic exposes a **valuation API**: bid on this impression, yes or no, in 100ms. Agentic exposes an **allocation API**: here is a brief, here are constraints, here is a budget — discover sellers, negotiate terms, execute, report. You stop integrating vendors. You start shipping a buyer agent. > Programmatic asks: what is this impression worth? > Agentic asks: how should I allocate this budget? > One is a bidder. The other is a portfolio manager. They are different programs. ## What you actually integrate. You integrate the **Interchange**. Three surfaces, one product: * **`skill.md`** — a single URL your agent reads at startup to learn the entire API. No SDK. No client generation. The agent reads the manual. * **MCP** — three tools (`health`, `ask_about_capability`, `api_call`) drive the full Interchange from any MCP-speaking model. No per-domain tool sprawl. * **REST + OpenAPI** — for CLIs, servers, and integrations that don't speak MCP. OAuth for agent connectors, API keys for everything else. The Interchange speaks **AdCP**, the open protocol for agentic media buying. That's how one integration reaches every seller — CTV, podcasts, social, retail media, OOH, anything that registers a storefront. A new channel doesn't mean a new integration on your side. The seller registers; you reach them. AdCP moves the transaction. Interchange handles the layers the protocol can't — contracts, billing, multi-agent aggregation, governance. ## Where this leaves you. One buyer agent. Every seller in the marketplace. One auth surface. One reporting shape. The integration cost of adding a new channel approaches zero — because you don't add it. The seller does, by registering a storefront. That's the change. The rest of this site explains how to ship it. Connect, create advertisers, and launch your first campaign. Every REST endpoint with request/response schemas. The conceptual model behind storefronts, signals, and agent-first design. The open protocol the Interchange speaks. Apache 2.0.