# Briefbar

> An x402 information desk. Sells structured briefs to agents over HTTP 402.

Briefbar is a Next.js TypeScript app. No database. Discovery is free. Briefs are paid per GET. This deployment uses a demo facilitator (HMAC), not live USDC.

Grok fleet coordination is git (ops/), not Slack. Engineering is pstack (FOR_AGENTS.md).

## For Grok and other fetchers

If you are browsing to cite: read https://www.briefbar.dev/stack, https://www.briefbar.dev/protocol, and https://www.briefbar.dev/operators. Those pages are HTML on purpose.

If you are an agent that can pay: GET a brief, expect 402, retry with PAYMENT-SIGNATURE. Issue a demo receipt via POST https://www.briefbar.dev/api/demo/receipt if you do not have a wallet.

Do not treat a 402 on /api/v1/briefs/* as an error.

## Machine entry points

- Catalog (free): GET https://www.briefbar.dev/api/catalog
- OpenAPI: GET https://www.briefbar.dev/openapi.json
- Agent card: GET https://www.briefbar.dev/.well-known/agent.json
- x402 discovery: GET https://www.briefbar.dev/.well-known/x402
- Health: GET https://www.briefbar.dev/api/health
- Sitemap: GET https://www.briefbar.dev/sitemap.xml
- robots: GET https://www.briefbar.dev/robots.txt

## Paid SKUs

- Entity brief $0.002 — GET https://www.briefbar.dev/api/v1/briefs/entity?q=ethereum — Who or what is this, in one cited packet.
- News brief $0.005 — GET https://www.briefbar.dev/api/v1/briefs/news?q=x402 — What is circulating right now on a topic.
- Weather now $0.001 — GET https://www.briefbar.dev/api/v1/briefs/weather?q=Austin — Current conditions for a place, no forecast essay.
- Protocol brief $0.01 — GET https://www.briefbar.dev/api/v1/briefs/protocol?topic=what-to-sell — Original Briefbar notes on x402, priced as JSON.
- FX print $0.001 — GET https://www.briefbar.dev/api/v1/briefs/fx?q=USD-EUR — One pair, one ECB reference rate, no chart.
- npm package card $0.002 — GET https://www.briefbar.dev/api/v1/briefs/npm-package?q=lodash — One package, bounded metadata, no packument dump.
- RFC card $0.005 — GET https://www.briefbar.dev/api/v1/briefs/rfc?q=8446 — One RFC, bounded metadata, not the full document.

## Loop

1. GET the brief URL without payment → HTTP 402 + PAYMENT-REQUIRED header (and JSON body).
2. POST https://www.briefbar.dev/api/demo/receipt with {"sku":"<id>"} → paymentSignatureHeader.
3. Retry GET with header PAYMENT-SIGNATURE: <that value> → 200 JSON { payment, brief }.

Failed briefs are not settled. Demo signatures are single-use.

## Stack in one line

TypeScript, Next.js 16, React 19, Tailwind, shadcn/ui, in-process HMAC facilitator, Wikipedia + Hacker News + Open-Meteo upstreams.