# GW8 Signal API (x402): agent payment risk checks + crypto market data
> Pay-per-call tools for AI agents: should-I-pay decisions (spend policy + x402 seller reputation), token verdicts, payment-rail costs, crypto market data. USDC on Base via x402 v2. Signal only, no trading, not financial advice.
> Agent guide with "use this when", examples, idempotency and receipt verification: GET /agents.md

## Start here (free)
- GET /api/brief/teaser — partial live brief: regime score x/4, green/red counts, top 3 dots (symbol+band only), simulated 7d hit-rate headline + upsells.
- GET /api/sample — Stage 1 statuses + core WaveTrend values (BTC/ETH/SOL/LINK/XRP).
- GET /agents.md — agent guide. GET /llms.txt — this file. GET /openapi.json — OpenAPI. GET /.well-known/x402 — resource fan-out.
- GET /pay.html — human wallet pay page (mobile-friendly).
- GET /track and GET /api/track — honest track record. Backtest is **simulated**. Live log accrues after deploy.
- GET /api/stats, /stats.html — request tallies + bots vs likely buyers (no PII). GET /api/proof/pubkey, GET /.well-known/gw8-receipt-key — signing / receipt key.

## Trust
- No charge on failure: verify -> build data -> settle; if the data or the settle fails, nothing is charged and nothing is returned.
- Signed receipts: every paid call returns a signed receipt your agent can keep as an audit trail. JSON body field `receipt` {endpoint, query, timestamp, response_sha256, tx, payer, payload, signature, pubkey_url} (Ed25519 over utf8(payload), key /api/proof/pubkey; `signed:false` if signing is not configured). Free check: GET/POST /api/receipt/verify. Headers: X-GW8-Receipt (base64url JSON: route, amount, tx, payer, issuedAt, bodySha256) + X-GW8-Receipt-Signature (Ed25519). Key: /.well-known/gw8-receipt-key.
- Safe retry: resending the same PAYMENT-SIGNATURE to the same URL within 15 min returns the same response (X-GW8-Replay: true), no second charge.
- Best value: POST /api/pass/day ($1.00) = 24h of every paid data endpoint via X-GW8-Pass.
- Raw USDC transfer + tx hash (X-Payment-Tx) is retired (410); pay with x402 only.
- GET /api/govcontracts/status, /api/kraken/listings/status, /api/rules/status, /api/seller/reputation/status — source health only (reputation status: which source is active (alchemy or blockscout) and is it reachable from GW8 right now; cached 60s).

## Menu tiers

### Starter
| Call | Price |
| --- | --- |
| GET /api/brief/teaser (free) | $0 |
| GET /api/sample (free) | $0 |
| GET /api/coin/{symbol} | $0.002 |
| GET /api/regime | $0.01 |
| GET /api/dots | $0.01 |

### Research
| Call | Price |
| --- | --- |
| POST /api/agent | $0.02 |
| GET /api/brief | $0.02 |
| GET /api/history (?pair=) | $0.05 |
| GET /api/flows/{symbol} | $0.02 |
| GET /api/kraken/listings | $0.02 |
| GET /api/rs | $0.02 |
| GET /api/rails (?amount=) | $0.002 |
| GET /api/verdict/{chain}/{address} | $0.01 |

### Agent payments
| Call | Price |
| --- | --- |
| POST /api/pay/should-i-pay | $0.02 |
| POST /api/spend/check | $0.02 |
| POST /api/seller/reputation | $0.01 |

### Access
| Call | Price |
| --- | --- |
| POST /api/pass/day | $1.00 |
| POST /api/brief/weekly/subscribe | $0.25 |
| POST /api/alerts/subscribe | $0.50 |

## Paid detail (what / when)
- POST /api/agent ($0.02): full Stage 1 regime + WaveTrend band dots on 66 Kraken 4h pairs.
- GET /api/regime ($0.01): Stage 1 detail (ETF flows, BTC support, alt breadth, Fear & Greed).
- GET /api/dots ($0.01): every green/red WaveTrend band dot (inner/outer) with wt1/wt2 and closes.
- GET /api/coin/:symbol ($0.002): WaveTrend 4h for one coin (cheapest).
- GET /api/history ($0.05): **simulated** 90-day hit-rate backtest (+4h/+24h/+3d). Not a live trade log.
- GET /api/brief ($0.02): once-per-day MT digest — regime, top 10 dots with strength, BTC/ETH/SOL flows. Free teaser: /api/brief/teaser.
- GET /api/verdict/:chain/:address ($0.01): token safety 0-100 (GoPlus + DexScreener). Automated screen, not a guarantee.
- GET /api/flows/:symbol ($0.02): Kraken large-print flows + WaveTrend (single venue).
- GET /api/kraken/listings ($0.02): new Kraken USD pairs (30d) + WaveTrend state.
- GET /api/rs ($0.02): relative strength (1w/1m returns, ranks, 0-100 score) on 66 Kraken pairs + sector scores and breadth.
- GET /api/rails ($0.002): cheapest/fastest rail now for ?amount= (Base USDC, XRPL, Tempo, Arc live fees; card = static estimate) + agent protocols per rail (x402/MPP/card networks; unconfirmed ones marked unverified).
- POST /api/pay/should-i-pay ($0.02): one call before an agent pays. Body {payment, policy, seller:{address and/or endpoint, lookbackDays}, sellerRules?:{onCaution, onUnknown: pay|ask_human|dont_pay (default ask_human), minScore}}. Runs the spend-policy check + seller reputation; returns verdict pay|dont_pay|ask_human (worst wins: spend deny or seller avoid -> dont_pay; needs_approval, caution, unknown, or recipientId != seller address -> ask_human), reasons, both sub-results and one signed decisionReceipt. Invalid bodies get 400 before payment; not charged if seller data is unavailable. MCP tool: should_i_pay.
- POST /api/spend/check ($0.02): spend-policy check before an agent pays. Body {payment, policy}. payment: amount (decimal string), currency, recipientId and/or recipientDomain, merchantCategory, chain, timestamp (ISO), agentId, memo. policy: currency, perTxLimit, rollingCap {limit, spentSoFar, windowHours=24}, allowedCategories, blockedCategories, allowList, denyList, onUnlisted (deny|needs_approval), allowedHours {start "HH:MM", end, timezone IANA, days}, allowedAssets, allowedChains, requireApprovalAbove. Returns decision allow|deny|needs_approval (deny beats needs_approval), reasons (rules that fired), every check, remaining limits, and an Ed25519-signed decisionReceipt bound to sha256 of your request. Stateless: nothing stored, you send spentSoFar. No FX: a payment in another currency than policy.currency is denied. Invalid bodies get 400 before payment. MCP tool: check_spend_policy. Not custody, does not move money.
- POST /api/seller/reputation ($0.01): x402 seller reputation before an agent pays. Body {address} (seller wallet on Base) and/or {endpoint} (x402 https URL; payTo read from its unpaid 402 challenge), optional lookbackDays (1-90, default 90). Reads public USDC transfers on Base (Alchemy Transfers API, keyless Blockscout fallback; newest 1000 transfers, max 90 days). Returns score 0-100, verdict trusted|caution|avoid|unknown, components (distinct organic paying buyers /30, wash share = self-transfers + round-trip payers /25, wallet age /15, top-payer concentration /20, 30-day organic USD volume /10), reasons, flags (self_transfers, round_trips, wash_majority, single_payer_repeating, payto_mismatch) and an Ed25519-signed reputationReceipt. Only canonical USDC counts (lookalike tokens and < $0.001 dust ignored). Deterministic, stateless, never pays anyone. Invalid bodies get 400 before payment; if the data source is down you are not charged. Heuristic, not a guarantee. MCP tool: check_seller_reputation. Free: GET /api/seller/reputation/status shows whether the data source is reachable (check before paying).
- POST /api/alerts/subscribe ($0.50): green-dot webhook alerts (HMAC). Body needs webhookUrl.
- POST /api/brief/weekly/subscribe ($0.25): 4 Monday webhook briefs.
- POST /api/pass/day ($1.00): 24h access via X-GW8-Pass (excludes alerts). Fair use 2000/day, 60/min.

## Payment
- x402 v2, USDC on Base (eip155:8453), asset `0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913`, payTo `0xB4527dccaC81eB73d4988A51a4cb1FBBF2C3CaBd`.
- Unpaid → **402** with PAYMENT-REQUIRED. Retry with PAYMENT-SIGNATURE.
- Discovery: /openapi.json, /.well-known/x402. CDP Bazaar indexes after first successful settlement.

## Honesty
- History/track **backtest** = simulated.
- Track **live log** starts empty until the first logged dot.
- Also live but not featured (see /openapi.json): /api/rules, /api/rwa, /api/govcontracts (DoD awards ≈ 90-day USAspending lag).
- Signal only — not financial advice, no trade execution.