# Reverse Agent API by reverse.captcha

> Pay-per-call security and web utilities for autonomous agents, paid in USDC on Base via x402. No account or API key. Failed fetches are never charged.

## When to use it

- You need proof of what a web page said at a point in time (evidence snapshot with a content hash).
- You need to know whether a source is fresh enough before relying on it.
- You want a verifiable identity for your agent (Ed25519 key registration and a signed BOT PASSPORT).

## Recipes (copy these)

### Snapshot a page as evidence ($0.03)
POST https://reversecaptcha.fun/v1/paid/evidence
body {"url":"https://example.com/article"}
-> {"ok":true,"final_url":"...","status":200,"sha256":"...","redirects":[...],"fetched_at":"...","title":"...","excerpt":"..."}

### Is this source fresh enough? ($0.01)
POST https://reversecaptcha.fun/v1/paid/freshness
body {"url":"https://example.com/news","max_age_seconds":86400}
-> {"ok":true,"freshness":"fresh|stale|unknown","is_within_max_age":true,"evidence_timestamp":"...","evidence_source":"html:time","age_seconds":5400}

### Register your agent identity ($0.01)
POST https://reversecaptcha.fun/v1/paid/register
body {"name":"My Agent","public_key":"-----BEGIN PUBLIC KEY-----\n...Ed25519 SPKI PEM...\n-----END PUBLIC KEY-----","capabilities":["fetch","summarize"]}
-> {"agent":{"id":"bot_...","tier":"agent"},"passport":"<signed BOT PASSPORT>"}

### Upgrade to the Pro tier ($0.05)
POST https://reversecaptcha.fun/v1/paid/tiers/pro
body {"agent_id":"bot_..."}

## How to pay (x402)

1. Call the endpoint; you get HTTP 402 with a PAYMENT-REQUIRED header (base64 JSON).
2. Sign a USDC (Base, eip155:8453) EIP-3009 transferWithAuthorization for the quoted amount to 0x87e8d821649a61815e4fa61d892fca13b7d07028 (any x402 client does this: x402-fetch, @x402/fetch, agentcash, FluxA wallet, Coinbase AgentKit).
3. Retry with header PAYMENT-SIGNATURE. If the target cannot be fetched you get 422 with "charged": false.

## Machine-readable

- OpenAPI: https://reversecaptcha.fun/openapi.json
- x402 discovery: https://reversecaptcha.fun/.well-known/x402
- Catalog: https://reversecaptcha.fun/v1/services
- Protocol: https://reversecaptcha.fun/.well-known/reverse-captcha