1AUTH→Validate API key, resolve agent_id
2IDEMPOTENCY→Deduplicate by idempotency key
3CONTENT_NEG→Accept/Content-Type negotiation
4SCHEMA_VALIDATION→Zod validation — reject malformed input
5TOOL_STATUS→Check tool exists & healthy
6CACHE→Redis lookup — return if cached (TTL per tool)
7RATE_LIMIT→Dual-bucket per agent per tool
8ESCROW→Verify x402/MPP payment — 402 if unpaid
9PROVIDER_CALL→Call upstream API (Amadeus, CoinGecko, DHL...)
10ESCROW_FINALIZE→Charge on success, refund on failure
11LEDGER_WRITE→Append-only financial record (PG transaction)
12CACHE_SET→Store response in Redis
13RESPONSE→Return normalized JSON to agent