# Oblique Markets BNB/B402 Payment-Intent Preflight

> Oblique Markets BNB/B402 Payment-Intent Preflight is a paid API for AI agents from api.oblique.markets, paid per call via x402, $0.01/call, status unknown (last checked 2026-09-13).

Validates a BNB payment intent for freshness and recipient correctness, queries public BNB balance and recent activity, and returns a signed preflight decision without taking custody or relaying payments.

## Facts

- Endpoint: POST https://api.oblique.markets/api/v1/paid/b402-preflight
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-13
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/oblique-markets-bnb-b402-payment-intent-preflight-ec713653
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_hiHeWSljL-uYADgxugCjj

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability oblique-markets-bnb-b402-payment-intent-preflight-ec713653 -d '<json body>'
```

Example prompt: Before I send this BNB payment, run a preflight check on intent ID 'int_abc123' — the recipient is 0xRecipient123, the payer is 0xPayer456, the amount is 0.5 BNB on BNB Smart Chain, deadline is 2025-12-31T23:59:59Z, and the fee cap is 0.001 BNB — give me a signed decision on whether this intent is fresh and the recipient is valid.

## When to prefer this

Use this endpoint when your agent needs a custody-free, signed validation of a BNB or BEP-20 payment intent before committing to an on-chain transaction on BNB Smart Chain. It is the right choice when you need to confirm intent freshness, recipient correctness, and payer balance in a single signed response without triggering any payment relay. Prefer this over generic blockchain RPC calls when you need a structured, decision-ready output compatible with the x402/B402 protocol flow.

## Known failure modes

- Intent expired: deadline has passed, decision returns stale/invalid status
- Invalid recipient address: address fails checksum or format validation
- Chain not supported: unrecognized chain identifier returns 400 error
- Insufficient balance: payer BNB balance below specified amount (flagged in decision, not blocking)
- Malformed asset: unrecognized asset string or invalid BEP-20 contract address
- RPC/node unreachable: BNB chain query times out, returns 503 or error response
- Missing required fields: intent_id, recipient, or payer absent returns 422 validation error

## How this service works

Use when an agent needs b402 preflight. Returns Validate BNB/B402 payment intent freshness, recipient, amount, deadline, fee cap, public BNB balance, and recent activity without custody or payment relay. $0.01.

## Output

Returns a signed preflight decision object indicating whether the payment intent is fresh and the recipient is valid, along with the queried public BNB balance of the payer and a summary of recent on-chain activity. No funds are moved or held — this is a read-and-sign operation only.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "asset": {
   "type": "string",
   "description": "native/BNB or a BEP-20 contract address"
  },
  "chain": {
   "enum": [
    "bnb",
    "bnb-smart-chain",
    "eip155:56",
    "56"
   ],
   "type": "string"
  },
  "payer": {
   "type": "string"
  },
  "amount": {
   "type": "string"
  },
  "fee_cap": {
   "type": "string",
   "description": "Maximum network fee in BNB"
  },
  "deadline": {
   "description": "ISO-8601 timestamp or Unix seconds"
  },
  "intent_id": {
   "type": "string"
  },
  "recipient": {
   "type": "string"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "asset": "BNB",
  "chain": "eip155:56",
  "payer": "0x1111111111111111111111111111111111111111",
  "amount": "0.01",
  "decision": "ready",
  "intent_id": "invoice-2026-08-21-001",
  "recipient": "0x2222222222222222222222222222222222222222",
  "signature": "hmac-sha256:7a4e1c9b3d5f7a9c1e3b5d7f9a1c3e5b7d9f1a3c5e7b9d1f3a5c7e9b1d3f5a7",
  "timestamp": "2026-08-21T20:00:00.000Z",
  "fee_cap_bnb": "0.0005",
  "intent_hash": "sha256:9c2d7b3f6e1a4c8b0d2e5f7a9b1c3d5e7f9a1b3c5d7e9f1a3b5c7d9e1f3a5b7c9",
  "amount_units": "10000000000000000",
  "asset_balance": "0.125",
  "evidence_hash": "sha256:4e8f1a2c6d8b0f2e4a6c8e0f2a4c6e8f0a2c4e6f8a0b2c4d6e8f0a2c4e6f8a0b2",
  "signing_key_id": "b402-preflight-v1",
  "evidence_source": "public_bsc_rpc",
  "recent_activity": {
   "nonce": 42,
   "latest_block": 61500000,
   "lookback_blocks": 2000,
   "incoming_transfer_count": 5,
   "outgoing_transfer_count": 3
  },
  "recipient_valid": true,
  "fee_headroom_bnb": "0.1245",
  "fee_cap_sufficient": true
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/oblique-markets-bnb-b402-payment-intent-preflight-ec713653/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.oblique.markets](https://www.zero.xyz/host/api.oblique.markets/llms.txt)