# Agents overview

> For people who build AI agents, crawlers and browser agents: how to get through a site protected by AgentGate on the site's terms.

This section is for people who run AI agents, crawlers or browser agents
that visit sites protected by AgentGate. Site operators will find the
matching configuration in [Agent policy for sites](/docs/agent-policy).

AgentGate does not try to keep agents out. It asks them to say who they
are, and then applies the site's policy to that identity. An agent that
signs its requests is never shown a human check.

## The five things to handle

| Step | What you do | Page |
| --- | --- | --- |
| 1. Identify | Sign every request with Web Bot Auth (Ed25519, RFC 9421) | [Sign requests](/docs/web-bot-auth) |
| 2. Discover | Read the site's tool manifest, `/.well-known/agentgate-tools.json` | [Declared tools](/docs/agent-tools) |
| 3. Pay, if asked | Answer `402 Payment Required` with a price offer | [Pay per crawl](/docs/pay-per-crawl) |
| 4. Hand off | When a check is needed, give your person a link or QR code | [Human handoff](/docs/human-handoff) |
| 5. Keep proof | Store the signed `AgentGate-Receipt` of each decision | [Signed receipts](/docs/agent-receipts) |

## What an unsigned agent gets

A User-Agent that names a known AI agent or crawler (`GPTBot`,
`ChatGPT-User`, `PerplexityBot`, …) without a valid signature is an
**unverified claim**. Depending on the site's policy it is challenged (the
default), blocked, or asked to pay. A browser agent driving a person's
Chrome without signing is scored like any other automation and is likely to
be asked for the press-and-hold check, which agents cannot and should not
pass: hand it to your person instead.

## Responses you should expect

| Status | Meaning | What to do |
| --- | --- | --- |
| `2xx` | allowed | keep the `AgentGate-Receipt` header |
| `401` | no valid signature or key | sign the request; check `created`, `expires`, `keyid`, nonce |
| `402` | a price applies | retry with `crawler-exact-price` or `crawler-max-price`, signed |
| `403` "not permitted" | the site's policy does not allow your agent this action | stop; ask the site operator |
| `403` / `428` with `handoff` | a person must complete a check | show `handoff.url`, poll `handoff.poll` |
| `429` | over your per-site quota | wait `Retry-After` (60 s) |

All codes: [Error codes](/docs/error-codes#agents).

## About the examples

The examples use AgentGate's built-in agent API, `POST /agent/submit`, and
its declared tool `send_message`. That endpoint exists on an AgentGate
instance whose operator has registered agent keys or key directories. On
customer sites, agents call the site's own routes through the
[gateway](/docs/gateway), which verifies the same signatures.