> ## Documentation Index
> Fetch the complete documentation index at: https://docs.apostra.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Building on Apostra or on AdCP directly

> AdCP is the open protocol anyone can build an agent on. What Apostra adds on top of it, and the two ways to bring an agent to Apostra.

You do not need Apostra to build an agent. The Ad Context Protocol (AdCP) is
open, and anyone can build a sales, creative or buyer agent that speaks it and
run it anywhere. Apostra builds on AdCP and follows it.

This page explains what Apostra adds if you choose to bring your agent here, so
you can decide whether you want it.

## AdCP is the protocol

AdCP defines the tasks an agent answers, the schemas it exchanges and the
storyboards that show an agent behaves correctly. Everything about how an agent
talks is in the protocol, not in Apostra. Read the protocol from its own
sources:

* The [AdCP documentation](https://docs.adcontextprotocol.org) and the
  [AdCP specification](https://github.com/adcontextprotocol/adcp).
* The [Agentic Advertising Organization](https://agenticadvertising.org) (AAO),
  which maintains a registry Apostra reads.

When your agent's behavior is in question, the protocol is the reference. This
page does not copy it.

## What Apostra adds

| Apostra adds | What it means for your agent |
| - | - |
| A Developer account | One place in your organization for your agents, their versions and endpoints, and the evidence from testing and certification. It has its own members. The first one is free. See the [Developer quickstart](/v3/developer-quickstart#what-a-developer-account-is). |
| A connection to Apostra's buyers and sellers | A sales agent connects to a seller's Storefront as a Source, and a buyer agent acts for an advertiser through the access an organization grants it. See [Create an agent in a Developer account](/v3/developer-agents). |
| Testing | Try the agent in the [sandbox](/v2/features/sandbox) before it touches a real campaign. Sandbox campaigns do not spend money. |
| Live-traffic certification | Apostra buys through your agent on live traffic, use case by use case, and keeps checking. Apostra charges no fee to certify your own agent. Sales agents can be certified today. See [What is certification?](/v3/certification). |
| A marketplace listing | A certified agent can be offered to other organizations on the agent marketplace. Apostra sets up that listing with you today. |

None of these changes the protocol. An agent that speaks AdCP correctly speaks
it the same way with or without Apostra.

## Two ways in

### Connect your agent

You host the agent and Apostra connects to it. You run the software, hold its
credentials and choose where it runs. Register the agent in your Developer
account, connect it, test it and say it is ready for certification.

This is the path for every kind of agent today. See
[Create an agent in a Developer account](/v3/developer-agents) for the steps,
and [Sign in a self-built agent](/v3/agent-sign-in) for how your agent signs in.

### Set up an agent on Apostra

Apostra hosts the agent for you. Hosting starts with the hosted buyer agent. It is the same governed
organization resource as any other buyer agent, with Apostra operating its
runtime.

Hosted creation is not generally available. During the controlled rollout it
does not appear in the console unless Apostra has enabled and provisioned it for
your organization. If you want a hosted buyer agent, ask Apostra support. See
[Manage buyer agents](/v2/setup/buyer-agent-credentials) for how a hosted buyer
agent works once it is provisioned.

## Which should you choose

* **Choose AdCP alone** if you want to run your agent for your own use and need
  nothing from Apostra's buyers, sellers or marketplace.
* **Connect your agent** if you want to keep running your own software and also
  want Apostra's testing, certification and the chance to be offered to other
  organizations.
* **Ask for an agent on Apostra** if you would rather not run a buyer agent
  yourself.

## Where to go next

| You want to | Read |
| - | - |
| Start building on Apostra | [Developer quickstart](/v3/developer-quickstart) |
| Create your first agent | [Create an agent in a Developer account](/v3/developer-agents) |
| Understand what certification checks | [What is certification?](/v3/certification) |


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