--- title: AgentStream: what to use when slug: exotel-agentstream/agentstream-what-to-use-when createdAt: 2026-08-12T09:40:08.901Z --- Short chooser for connecting Voice AI over [Exotel AgentStream.](https://docs.exotel.com/exotel-agentstream/connect-voice-ai-api) There are **two control models**: | **Model** | **How call logic is defined** | **Typical entry** | | ----------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------- | | **Flow (App Bazaar)** | Dashboard applets (Voicebot, Stream, Connect, Passthru, Gather, Greeting) | Exophone → Appbazaar flow, Voicebot applet or Passthru/ Connect Applet with Url | | **ExoML (Programmable Voice APIs)** | Your code reacts to **gRPC leg events** and issues **leg actions** (start\_stream, start\_say, start\_play, hangup, bridge, …). **No App Bazaar flow required.** | Number attached to gRPC endpoint (inbound), or POST /legs (outbound) | Your bot WebSocket (AgentStream) is the same either way. Choose the **telephony control plane**, not a different bot protocol. ## Quick chooser | **You need…** | **Use** | | ------------------------------------------------------------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------- | | Outbound: answer → bot only | [Connect Voice AI API](https://docs.exotel.com/exotel-agentstream/connect-voice-ai-api) | | Outbound: answer → bot with custom routing logics via applets: Voicebot applet and then / IVR / greeting / DTMF / agent handoff via connect applet in Exotel | [Connect Voice AI with Flow API](https://docs.exotel.com/exotel-agentstream/connect-voice-ai-with-flow-api) | | Outbound or inbound: full runtime control in code, per-call stream URL, parallel greeting while bot connects | [ExoML / Programmable Voice APIs](https://docs.exotel.com/exotel-agentstream/programmable-voice-apis-with-agentstream) | | Inbound: dashboard flow with Voicebot applet | Assign virtual number (Exophone) to an **App Bazaar flow** that includes **Voicebot applet** | | Inbound: no flow — events to your app, you drive the call | Attach virtual number to a **gRPC endpoint** (ExoML / Programmable Voice) | ## Outbound ### 1. Connect Voice AI API — simplest outbound **Docs:** [Connect Voice AI API](https://docs.exotel.com/exotel-agentstream/connect-voice-ai-api) **What happens:** Your API dials the customer. On answer, Exotel opens bidirectional WSS to StreamUrl. **Use when:** - Campaigns, surveys, reminders — bot is the whole experience - No IVR, no compliance applet, no agent transfer in Exotel - Fixed bot URL is fine in the request (StreamUrl + StreamType=bidirectional) **Not for:** Menus, disclosure before bot, bot→human, or per-leg programmable actions. :::BlockQuote Your API → dial customer → answer → AgentStream WSS ↔ bot ::: ### 2. Connect Voice AI with Flow API — outbound + App Bazaar journey **Docs:** [Connect Voice AI with Flow API](https://docs.exotel.com/exotel-agentstream/connect-voice-ai-with-flow-api) **What happens:** Same connect call, but Url points at an App Bazaar flow. After answer, applets run. When the flow hits **Voicebot** / **Stream**, Exotel opens WSS. Stream URL is configured **in the applet**, not in the API body. **Use when:** - Compliance greeting → bot - IVR / DTMF → bot - Bot → Connect (human) or Passthru (your system) - Unidirectional Stream for assist / transcription **Not for:** Pure “answer → bot” (use Connect Voice AI), or code-owned per-leg control (use ExoML). :::BlockQuote Your API → dial customer → answer → App Bazaar flow → Voicebot/Stream → WSS ↔ bot ::: **Common flow patterns:** Greeting → Voicebot · Gather → Voicebot · Voicebot → Connect · Voicebot → Passthru ### 3. ExoML (Programmable Legs) — outbound in code **Docs:** [Programmable Voice APIs with AgentStream](https://docs.exotel.com/exotel-agentstream/programmable-voice-apis-with-agentstream) · [ExoML introduction](https://docs.exotel.com/voice-apis/exoml-introduction) **What happens:** You POST /legs to dial the customer, receive events on your **gRPC** leg\_event\_endpoint, then issue leg actions yourself (e.g. start\_stream, optional start\_say / start\_play). **Use when:** - Stream URL / routing decided per call at runtime - Parallel filler while bot connects (sales / collections “instant feel”) - You want application-owned call logic, not a dashboard flow | **Scenario** | **Pattern** | | ----------------------------------- | ---------------------------------------------------------------------------------------------------------------- | | Bot-first / tech support | leg\_answered → start\_stream | | Sales / collections / CC simulation | leg\_answered → start\_stream **+** short start\_say / start\_play → on stream\_started → stop\_say / stop\_play | :::BlockQuote Your API → POST /legs → gRPC events (connecting / ringing / answered)   → your app: start\_stream (+ say/play) → AgentStream WSS ↔ bot ::: ## Inbound Inbound has **two separate paths**. Do not mix them with the same mental model. ### A. Flow-based inbound (App Bazaar + Voicebot applet) **What happens:** Customer dials your Exophone. The number is linked to an **App Bazaar flow**. Applets execute in the dashboard-defined order. **Voicebot** opens bidirectional AgentStream to your bot. **Use when:** - You want visual / applet-based journeys (Voicebot, greeting, IVR, bot, agent handoff) - Same patterns as Connect-with-Flow outbound, but the customer dials in Customer → Exophone → App Bazaar flow → Voicebot → WSS ↔ bot **Setup:** Procure Exophone → assign **Voice URL / flow** → include Voicebot (and optional Connect / Passthru / Gather). ### B. ExoML programmable inbound (no App Bazaar flow) **What happens:** Customer dials your Exophone. The number is attached to a **gRPC endpoint** (Programmable Voice / Legs), **not** to an App Bazaar flow. Exotel pushes leg events to your gRPC service. **Your application is the flow** — you answer/control the leg with **leg actions** (start\_stream, say, play, gather, bridge, hangup, …). **Use when:** - Call logic must live entirely in code - Per-call dynamic stream URL, A/B routing, CRM-driven branching - Same ExoML action model as outbound Legs (inbound or outbound legs) :::BlockQuote Customer → Exophone (attached to gRPC) → gRPC leg events → your app   → leg actions (start\_stream, say/play, …) → AgentStream WSS ↔ bot ::: **Setup:** Implement gRPC event endpoint → register it → attach Exophone to that gRPC endpoint → on inbound events, issue leg actions. ExoML inbound does **not** require a Voicebot applet or App Bazaar flow. The programmable “flow” is the sequence of leg actions your service sends in response to gRPC events. ## Side-by-side | | **Connect Voice AI** | **Connect + Flow** | **ExoML (Legs)** | **Inbound Flow + Voicebot** | **Inbound ExoML** | | --------------------------------- | -------------------- | ---------------------- | -------------------------------------------------- | --------------------------- | --------------------------- | | Direction | Outbound | Outbound | Outbound **and** inbound | Inbound | Inbound | | Control plane | Single connect API | App Bazaar applets | gRPC events + leg actions | App Bazaar applets | gRPC events + leg actions | | App Bazaar flow | **No** | Yes | **No** | Yes | **No** | | Where WSS URL is set | API StreamUrl | Voicebot/Stream applet | start\_stream action | Voicebot/Stream applet | start\_stream action | | Parallel greeting while bot warms | Bot-owned | Flow Play applet | start\_say / start\_play + stop on stream\_started | Bot-owned | Same ExoML say/play pattern | | Best for | Simple outbound bot | Multi-step outbound | Code-first, dynamic control | Dashboard inbound journeys | Code-first inbound | ## Decision tree :::BlockQuote Who starts the call? │ ├─ Customer dials (inbound) │ ├─ Want dashboard applets (Voicebot,Passthru, Connect)? │ │ └─ Exophone → App Engine flow → Voicebot │ └─ Want logic in your app (no flow)? │ └─ Exophone → gRPC endpoint → leg actions (ExoML) │ └─ You dial (outbound) ├─ Bot only, fixed StreamUrl? │ └─ Connect Voice AI API ├─ Need Exotel flow (Voicebot applet/Passthru / agent handoff)? │ └─ Connect Voice AI with Flow API └─ Need gRPC + leg actions / dynamic stream / parallel say-play? └─ ExoML Programmable Legs API ::: ## Same bot, four front doors | **Entry** | **Who dials** | **Control** | **Who configures WSS** | | ---------------- | --------------------- | ------------------ | ---------------------- | | Connect Voice AI | Your API | Connect API | StreamUrl in API | | Connect + Flow | Your API | App Bazaar | Voicebot/Stream applet | | ExoML outbound | Your API (POST /legs) | gRPC + leg actions | start\_stream body | | Inbound Flow | Customer | App Bazaar | Voicebot/Stream applet | | ExoML Inbound | Customer | gRPC + leg actions | start\_stream body | ## References - [Connect Voice AI API](docId\:oWtjaGRpfWe8dJHjIQSlI) - [Connect Voice AI with Flow API](docId\:YKd82KkkOVAVq4vrngHpe) - [Programmable Voice APIs with AgentStream](docId\:iP28BOjsUUU9kz1Pu1Miv) - [ExoML — Introduction](docId\:Ju_t9ACidAdHKkOAfYdWp) - [AgentStream developer guide](https://developer.exotel.com/docs/agentstream/developer-guide) - [Implementing Your gRPC Endpoint for Real-Time Call Events](docId\:ah1nMJ4tFRVxBU6FHHzEB)