Dexter Adds a Phone Number — Dial In, Search APIs, Pay with Your Voice
Call +1 (561) 940-2402 and talk to Dexter. Search 765+ paid APIs, pay for calls with USDC, get results read back — no account needed. Linked phone callers are verified automatically; everyone else can transact up to $0.10 freely.
An Agent That Picks Up the Phone
Dexter, the facilitator behind millions of x402 settlements, today launches Dexter Phone — a live voice line at +1 (561) 940-2402 where anyone can talk to Dexter, search the x402 marketplace, and pay for API calls in real time.
No account required. No app to download. Dial the number, ask for what you need, and Dexter handles the search, the payment, and the response while you're still on the line.
For users who link their phone number at dexter.cash/profile, Dexter recognizes them on the call, greets them by name, remembers previous conversations, and can access their managed wallet immediately — no verification codes needed.
Anyone Can Call
The baseline experience requires nothing — just a phone. Call the number and Dexter can:
- Search the marketplace — "Find me a sentiment analysis API for SOL under ten cents"
- Pay for and call APIs — Dexter pays with USDC through session-funded OpenDexter wallets and reads you the result
- Transact up to $0.10 without verification — Small transactions go through immediately for everyone
- Answer questions — About Dexter, x402, the marketplace, whatever
This works for anyone. No Dexter account. No wallet. No setup.
Registered Users Get More
Users who link their phone number unlock additional capabilities:
- Dexter knows who you are — Greeted by name, account context loaded automatically
- Instant wallet access — Linked phone = verified identity. No SMS codes, no friction. STIR/SHAKEN attestation provides the trust layer.
- Conversation memory — Dexter remembers what you talked about last time and references it naturally
- Persistent spend sessions — Fund once, use across multiple calls
Linking takes ten seconds at dexter.cash/profile. But it's optional.
Real-Time Voice, Not Transcribe-and-Respond
Dexter Phone isn't a voice-to-text wrapper around a chatbot. The system bridges Twilio's media streams directly to OpenAI's Realtime API over WebSocket — audio flows bidirectionally with no intermediate transcription step. Dexter hears, thinks, and speaks in the same stream.
The result is a conversation that feels natural:
- Semantic turn detection — Dexter knows when you're done talking vs. pausing to think
- Interruptible — Start talking and Dexter stops immediately
- Low latency — Responses begin in under a second
- Natural filler — "Let me check on that..." while tools execute, not dead silence
- SMS companion — Links, addresses, and detailed results get texted to you mid-call. If SMS isn't available, Dexter reads the key info aloud instead.
Under the Hood
| Layer | Stack |
|---|---|
| Voice | OpenAI Realtime API (gpt-realtime-1.5) + semantic VAD |
| Telephony | Twilio Programmable Voice + Media Streams (WebSocket) |
| Agent tools | Dexter Open MCP Gateway — x402_search, x402_pay, x402_fetch |
| Caller lookup | STIR/SHAKEN attestation (used for verification decisions) + Dexter API phone-to-account resolution |
| Wallet verification | Linked phone = auto-verified. Unregistered callers: SMS OTP only above $0.10 USDC cumulative |
| Memory | Per-caller call log with topic summaries and tool usage history |
| Payments | x402 v2 settlement via Dexter Facilitator across Solana + 5 EVM chains |
Built with the @openai/agents SDK and TwilioRealtimeTransportLayer extension. Each inbound call spawns a dedicated RealtimeSession with dynamically injected caller context and tool set.
Caller Identity
When a call comes in, Dexter resolves the caller through four paths:
- Registered + wallet — Verified by linked phone number. Greeted by name, full wallet access, no codes needed. Weak STIR/SHAKEN attestation adds extra caution for high-value operations.
- Registered, no wallet — Recognized but limited to marketplace search and session-funded calls.
- Not registered — Full marketplace access and session-funded API calls. Transactions under $0.10 go through without verification. Above that, SMS OTP required.
- Unknown caller ID — Marketplace and session-funded calls still work. Wallet features and SMS tools unavailable. Dexter suggests calling back with caller ID enabled.
Call history persists across sessions. The third time you call about Solana sentiment data, Dexter knows that's your thing.
Security
Voice is inherently less controlled than an authenticated web session. The design accounts for that:
- No auth needed for search — Marketplace tools work for everyone, no verification required
- Linked phone = verified — Phone-to-account linking provides identity. STIR/SHAKEN attestation adds a trust signal.
- $0.10 free tier — Unregistered callers can transact small amounts without any verification
- SMS OTP for larger amounts — Above $0.10 cumulative, unregistered callers verify via 6-digit code
- No secrets over voice — Private keys, seed phrases, and full balances are never spoken. Sensitive info goes via SMS when available.
- Graceful SMS fallback — If text delivery fails during beta, Dexter reads essential info aloud instead of blocking the call