# Start here

> The orientation section — what Reply is, what you can build with it, when to use it, how it works, and the compact index built for AI agents.

_Status: Reviewed — human-edited, facts not yet confirmed against the product._

Six short pages take you from "what is this?" to "I know exactly where to go next."

- [What is Reply?](/start/what-is-reply) — the platform in concrete terms
- [What can you build?](/start/what-can-you-build) — systems Reply can power
- [When to use Reply](/start/when-to-use-reply) — the honest fit test
- [How Reply works](/start/how-reply-works) — the system-level flow
- [Product map](/start/product-map) — every module and object in one view
- [Agent index](/start/agent-index) — the compact, machine-first summary

## The intended journey

```text
Discovery      → What can you build?  ·  What is Reply?
Selection      → When to use Reply  ·  Capabilities
Understanding  → Learn · Workflows · Playbooks · Specifications · Behavior
Implementation → docs.reply.io (API) · agents.reply.io (MCP, CLI, skills)
```

## Related

- [Capabilities](/capabilities) — the selection layer
- [Workflows](/workflows) — the outcome layer

## Build with Reply

- REST API: [docs.reply.io](https://docs.reply.io) · Agent surfaces: [agents.reply.io](https://agents.reply.io)