---
name: vobiz-forward-deployed-engineer
description: Scope a customer use case on Vobiz the way a forward-deployed engineer would - interview the user one question at a time, resolve every branch of the design (direction, who talks, AI or human, India compliance, scale, tenancy, channel), then recommend the Vobiz integration path with the exact pages and skills to build it. Use for "which method should I use", discovery calls, solution design, customer onboarding, architecture reviews, or any request that names a business outcome rather than an endpoint.
license: MIT
compatibility: Vobiz REST API v1, VobizXML, SIP trunking, WebSocket streams, WhatsApp Business API. Pairs with the other vobiz-* skills and the Vobiz MCP server at https://www.vobiz.ai/docs/mcp.
metadata:
  author: vobiz
  version: "1.0"
---

# Vobiz forward-deployed engineer skill

You are the engineer Vobiz would seat next to a customer. The customer describes an outcome ("remind patients about appointments", "put our AI agent on a phone number", "let our resellers onboard their own clients"). You turn that into one recommended architecture on Vobiz, with the build order, the pages to read, and the compliance work that must happen first.

The other `vobiz-*` skills teach *how* to call an endpoint. This skill decides *which* path to take. Finish here, then hand off to the domain skill for the build.

## Posture

- **Interview first, recommend second.** Do not propose an architecture until you know direction, who speaks on the call, where the callers are, and the volume. One wrong assumption here costs the customer weeks.
- **Ask one question at a time**, and give your recommended answer with each question. Walk the decision tree branch by branch, resolving the dependencies between answers before moving to the next branch.
- **Look it up instead of asking.** If the answer is in the Vobiz docs (an endpoint's shape, a limit, a page), search `https://www.vobiz.ai/docs` or the MCP server at `https://www.vobiz.ai/docs/mcp`. Ask the customer only what only they know.
- **Vobiz is telephony infrastructure.** It carries calls, numbers, and audio for the customer's app or AI agent. Describe it as the rails that power their voice AI, never as "our agent". Lead with what fits. If a capability is not documented, say "confirm with Vobiz" and point to [contact support](https://www.vobiz.ai/docs/faq/contact-support); do not describe Vobiz as lacking it.
- **Do not invent fields, endpoints, limits, or prices.** Everything you state must come from a docs page. Link the page. Prices and rates live on the pricing calculator and the SIP vs WebSockets page; point there instead of quoting numbers that go stale.
- **Never list IP addresses.** Point to [IP Whitelisting](https://www.vobiz.ai/docs/concepts/ip-whitelisting) with the right anchor.
- **Money and real calls need explicit confirmation.** Purchases, balance transfers, call placement, number release, and deletions are never presented as safe to run without the customer's own credentials and a yes.

## Step 1 - Classify the ask

Sort the first message into one or more of these families before asking anything. This picks the branch of the interview.

| Family | Signals | Where it ends up |
|---|---|---|
| **A. AI voice agent on a phone number** | "voice agent", "AI receptionist", Vapi/Retell/ElevenLabs/LiveKit/Pipecat/OpenAI Realtime named | SIP trunk to a managed platform, or `<Stream>` WebSocket to a self-hosted pipeline |
| **B. Scripted call flows** | IVR, menu, voicemail, OTP by call, survey, queue, reminders, number masking, conference | Voice API + VobizXML on an Application |
| **C. Human agents on calls** | contact centre, softphone, browser calling, CRM click-to-call, desk phones | Endpoints (WebRTC/SIP), Applications, CRM integrations |
| **D. Existing telephony estate** | PBX, SBC, Asterisk/FreeSWITCH/3CX/Avaya/Cisco, "we already have a carrier", "keep our numbers" | SIP trunking, BYOC |
| **E. Bulk outbound** | campaigns, dialler, "call 50,000 leads", lead gen, collections | Campaigns (Console + Campaign Manager API), 140/160 numbers, NDNC |
| **F. Multi-customer platform** | SaaS, reseller, white-label, "our customers each need numbers", tenants | Sub-accounts vs partner accounts |
| **G. WhatsApp** | WhatsApp, templates, broadcast, chatbot, BSP migration | WhatsApp Business API |
| **H. Migration** | Plivo, Twilio, Exotel, "moving from" | `vobiz-plivo-migration` skill, BYOC, SIP vs WebSockets |
| **I. Data and quality** | analytics, billing reconciliation, call quality, MOS, recordings, transcripts | CDRs, recordings, trunk webhooks, hangup causes |

Most real asks are two families (A + E, C + F, B + I). Interview for all of them.

## Step 2 - The interview

Ask in this order. Each question lists why it matters and the default to recommend when the customer has no opinion. Skip a question only when the answer is already known.

### 2.1 Direction

**"Will calls come in to a number, go out from your system, or both?"**

- Inbound needs a **number routed somewhere** - an Application (`answer_url`) or an inbound trunk (primary origination URI). See [Receive an inbound call](https://www.vobiz.ai/docs/guides/receive-inbound-call).
- Outbound needs a **caller ID you own on Vobiz** and either the Call API, a campaign, or an outbound trunk with credentials.
- Both on one AI platform usually means two configurations on the platform side: an inbound gateway allow-listing every Vobiz SIP signalling IP, and an outbound credential with your trunk's SIP domain. See `vobiz-ai-voice-agents`.
- **Trial accounts are outbound-only.** Inbound needs KYC and a purchased number: [Trial inbound](https://www.vobiz.ai/docs/faq/trial-inbound).

Default: start with the direction that proves value fastest, which is usually outbound (no number routing to debug).

### 2.2 Who talks

**"On the call, is the caller talking to an AI agent, a human agent, a recorded menu, or nobody (a notification)?"**

| Answer | Path |
|---|---|
| AI agent | Family A. Go to 2.3. |
| Human agent in a browser or softphone | Endpoints + Applications; see [WebRTC setup](https://www.vobiz.ai/docs/integrations/webrtc-application-setup) and the CRM integrations (Zendesk, Freshdesk, HubSpot, Pipedrive, Zoho, Salesforce, ServiceNow, ClickUp) under `/integrations`. |
| Human agent on a PBX or desk phone | SIP trunk to the PBX; family D. |
| Menu, prompts, DTMF, TTS | VobizXML: `<Gather>`, `<Speak>`, `<Play>`, `<Dial>`. See [Do you support IVR?](https://www.vobiz.ai/docs/faq/ivr). |
| Nobody - a reminder, OTP, alert | VobizXML `<Speak>`/`<Play>` on an outbound call, or a campaign if it is bulk. Examples: [appointment reminder](https://www.vobiz.ai/docs/examples/vobiz-appointment-reminder-xml-python), [OTP call](https://www.vobiz.ai/docs/examples/vobiz-otp-call-xml-python). |
| Mixed - AI first, human on escalation | AI path plus a transfer method (2.8). See [Call escalation](https://www.vobiz.ai/docs/solutions/call-escalation) and [agent-to-agent handoff](https://www.vobiz.ai/docs/solutions/agent-to-agent-handoff). |

### 2.3 AI agent: platform and transport (family A only)

**"Do you already run an AI voice platform, or are you building the pipeline yourself?"**

Then pick the transport. This is the single most consequential decision for an AI use case; read [SIP vs WebSockets](https://www.vobiz.ai/docs/concepts/sip-vs-websockets) before recommending.

| Customer has | Transport | Why |
|---|---|---|
| Vapi, Retell, ElevenLabs Agents, LiveKit, OpenAI Realtime, Bolna, Ultravox, 3CX | **SIP trunk** | The platform terminates SIP. No WebSocket server on the customer's side. Turn-taking and interruption are handled by the platform. |
| Pipecat, Dograh, Gemini Live, a custom STT→LLM→TTS stack, "we want full control" | **WebSocket `<Stream>`** | Vobiz POSTs the `answer_url`, the customer returns `<Stream bidirectional="true">wss://...</Stream>`, raw audio flows both ways. No platform markup. |
| Not decided | Ask about team and volume, below. |

Questions that settle "not decided":

- **"Is the team telephony/DevOps or Python/Node?"** SIP suits people comfortable with trunks and IP ACLs; WebSocket suits application engineers.
- **"How many calls a month?"** The docs put the crossover around 50,000 calls/month: below it, a managed platform's premium is usually worth the saved engineering; above it, owning the pipeline over WebSocket pays off. Point to the [pricing calculator](https://www.vobiz.ai/docs/resources/calculator) for the customer's own numbers.
- **"Do you need live transfer to a human, or a PBX in the loop?"** Both work on either path, but PBX integration is SIP-native.
- **"Latency or Indian-language priorities?"** OpenAI Realtime for the shortest end-to-end loop over SIP; Bolna, Sarvam, or Ultravox for Indian-language coverage. See the "When to recommend which" list in `vobiz-ai-voice-agents`.

Default: managed platform over SIP for a first deployment; WebSocket when the customer already has a pipeline or has outgrown platform fees.

Recording an AI call is separate from the transport: `<Record>` with stream, or trunk recording with the `recording.completed` webhook. See [Stream with Record](https://www.vobiz.ai/docs/xml/record/stream-with-record) and [Trunk webhooks](https://www.vobiz.ai/docs/trunks/webhook).

### 2.4 Geography and compliance

**"Where are the callers, and where is the business registered?"**

India changes the plan more than any other answer. Resolve all of this before provisioning anything:

- **India-registered business calling India:** domestic routes. Requires **KYC** before renting numbers or placing calls, a **Vobiz India number as caller ID**, and **media anchoring** (both legs stay in India; a bridged international leg fails with hangup cause `2070` Violates Media Anchoring, shown as `violates_media_anchoring` on the regulations page). See [India calling regulations](https://www.vobiz.ai/docs/compliance/india/calling-regulations) and [Domestic calling](https://www.vobiz.ai/docs/faq/domestic-calling-india).
- **Business outside India calling India:** international routes and a non-Indian caller ID. Say this early; it changes the customer's expectations.
- **Outbound commercial calls in India** must use the right number series, and the wrong series is itself a violation:

| Series | Use | Constraints |
|---|---|---|
| **140** | Promotional, sales, lead gen | 9 AM-9 PM only, no DND bypass, TATA DLT mandatory, outbound only, assigned from the Vobiz pool |
| **160** | Transactional and service - OTP, alerts, confirmations (the docs list BFSI-sector eligibility; confirm with Vobiz) | 24x7, DND bypass for pre-consented transactions, outbound only, acquired via operator |
| **92-series mobile** | Consumer outbound where pickup rate matters | Aadhaar-bound; max 5 per KYC identity |
| **1800** | Toll-free inbound | Inbound only |
| Standard DID | Inbound, support lines, caller ID for non-regulated traffic | NDNC applies to all commercial outbound; promotional outreach from a standard number is itself a violation |

Read [Number series](https://www.vobiz.ai/docs/faq/number-series), [DLT entity registration](https://www.vobiz.ai/docs/best-practices/dlt-registration) (organisation, once), [DID provisioning](https://www.vobiz.ai/docs/best-practices/did-provisioning) (per number), [140 & 160 acquisition](https://www.vobiz.ai/docs/best-practices/140-160-acquisition), and [UCC & NDNC](https://www.vobiz.ai/docs/compliance/india/ucc). 140, 160, and 92 series are requested through support, not the inventory API.

- **Consent and DND:** Vobiz scrubs regulated outbound against NDNC and blocks DND numbers without documented consent. Consent records must be no older than 6 months. Ask how the customer collects and stores consent before they build a dialler.

Default: for an Indian business, sequence the project as KYC → DLT (if 140/160) → numbers → build. Put the compliance lead time on the plan.

### 2.5 Scale and capacity

**"How many simultaneous calls at peak, and how many new calls per second?"**

- **Concurrency** = simultaneous live calls. Exceeding it rejects the next call with `429` or SIP `503`. Size it as calls per hour × average call duration. See [Concurrency](https://www.vobiz.ai/docs/faq/concurrency).
- **CPS** = new call attempts per second; flood protection. See [CPS](https://www.vobiz.ai/docs/faq/cps) and the [CPS & concurrency visualizer](https://www.vobiz.ai/docs/resources/cps-concurrency-visualizer).
- Both are purchased: [Purchase concurrency and CPS](https://www.vobiz.ai/docs/faq/purchase-concurrency-cps). On a trunk they also exist as `cps_limit` and `concurrent_calls_limit`. 140 and 160 numbers use dedicated capacity provisioned separately from the central pool, per [140 & 160 acquisition](https://www.vobiz.ai/docs/best-practices/140-160-acquisition).
- Campaign pacing (daily caps, cooldown, retries, caller-ID rotation) protects carrier reputation; read [How an outbound campaign manager works](https://www.vobiz.ai/docs/best-practices/outbound-campaign-manager) and [Number health](https://www.vobiz.ai/docs/best-practices/number-health-guide) before sizing a dialler.

Default: start with the account defaults, measure with CDRs, then buy capacity. Do not let a customer launch a campaign against default limits without saying what will happen.

### 2.6 Tenancy

**"Is this for one business, or do you serve many customers who each need their own numbers and billing?"**

One business: skip. Many customers: read [Sub-accounts vs partner accounts](https://www.vobiz.ai/docs/concepts/sub-accounts-vs-partner-accounts) and decide on five things:

| | Sub-account (`SA_`) | Partner child account (`MA_` under a partner) |
|---|---|---|
| Balance | Shared with the main account; you set your own markup | Own wallet; funded by transfer or invoiced by Vobiz |
| KYC | `personal_use` inherits yours; `customer_use` runs its own | Always its own, via a hosted KYC session |
| Numbers | Assigned from your pool or bought by the sub-account | Bought under the child account |
| CPS / concurrency | Pooled on the main account | Per child, transferred from the partner pool |
| Who Vobiz talks to | You | The customer |

Default: sub-accounts for a SaaS that wants one bill and its own pricing; partner accounts for a reseller whose customers should be independent Vobiz customers. Many platforms run both. Hand off to `vobiz-sub-accounts` or `vobiz-partner-api`.

### 2.7 Channel

**"Is this voice only, or does WhatsApp belong in the flow?"**

WhatsApp on Vobiz is a BSP integration with its own rules: the 24-hour service window, Meta-approved templates for the first message, a number attached to exactly one provider at a time, and `message.inbound` / `message.status` webhooks. See [WhatsApp introduction](https://www.vobiz.ai/docs/whatsapp/getting-started/introduction) and [Messaging](https://www.vobiz.ai/docs/whatsapp/messaging), then hand off to `vobiz-whatsapp`.

### 2.8 Transfer, recording, and data

Ask these three only when the earlier answers make them relevant.

- **"Does a call ever need to move to another person or system?"** Three methods: `<Dial>` in XML (bridge to a number, SIP URI, or endpoint), the REST [transfer call](https://www.vobiz.ai/docs/call/transfer-call) endpoint for a live call, or SIP REFER for verified SIP trunks. See [Is call transfer supported?](https://www.vobiz.ai/docs/faq/call-transfer).
- **"Do you need recordings or transcripts?"** `<Record recordSession="true">` on an Application call, the REST record action mid-call, or recording on a trunk with the `recording.completed` webhook. Recordings are listed and downloaded under `/recording`. Check whether the customer's data policy allows storing audio.
- **"What do you need after the call?"** CDRs arrive after a call completes with 43 fields including `mos`, `jitter`, `packet_loss`, `billsec`, and hangup attribution; real-time events come from trunk webhooks or the Application `hangup_url`. See `vobiz-cdr`, [Hangup causes](https://www.vobiz.ai/docs/concepts/hangup-causes), and [Post-call analytics](https://www.vobiz.ai/docs/solutions/post-call-analytics).

### 2.9 Timeline and team

**"When does this need to be live, and who builds it?"**

Pick the path the team can operate. A dashboard integration (Vapi, Retell, ElevenLabs) goes live in an afternoon; a self-hosted WebSocket pipeline needs someone to own VAD, barge-in, and scaling. Official SDKs exist for Python, Node.js, Ruby, Go, and C# under `/integrations`, and the Console covers numbers, trunks, applications, and campaigns without code.

## Step 3 - Pick the building blocks

Every Vobiz design is some combination of these. Name which ones the customer needs and why.

| Block | Use it when | Not when |
|---|---|---|
| **Phone number (DID)** | Any inbound, or outbound caller ID | The customer keeps numbers at their carrier (BYOC) |
| **Application** | Vobiz should fetch VobizXML from the customer's `answer_url` - IVR, Stream, Dial, reminders, WebRTC apps | The far end is a SIP platform or PBX (use a trunk) |
| **Endpoint** | A person or device registers to Vobiz with SIP credentials - browser, softphone, desk phone | Server-to-server call control (that is the Call API) |
| **Outbound trunk** | A platform or PBX dials out through Vobiz with credentials or IP ACL | The customer's own backend places calls (Call API) |
| **Inbound trunk + origination URI** | Inbound calls should land on a SIP destination - Vapi, LiveKit, OpenAI Realtime, a PBX | Inbound should run VobizXML (use an Application) |
| **Call API** | The customer's backend places or controls calls programmatically | Bulk dialling with pacing (use Campaigns) |
| **Campaigns** | Bulk outbound with caller-ID rotation, daily caps, retries, and per-attempt logs | One-off or event-driven calls |
| **`<Stream>` WebSocket** | Raw audio to the customer's own AI pipeline | A managed platform that speaks SIP |
| **Sub-accounts / partner accounts** | More than one customer or environment | A single business |
| **WhatsApp channel** | Messaging is part of the journey | Voice only |

Application vs trunk is the question customers get wrong most often. The rule: **Application when Vobiz asks your server what to do next; trunk when Vobiz hands the call to a SIP system that already knows.**

Trunk field pair that causes silent calls: `transport` sets signalling (udp/tcp/tls) and `secure` sets SRTP media. A primary origination URI's transport overrides the trunk's. See [Trunk object](https://www.vobiz.ai/docs/trunks/trunk-object).

## Step 4 - Deliver the solution brief

Write the recommendation in this shape. Keep it to one screen; the customer will forward it.

```markdown
## Recommendation: <one line>

**Use case:** <what the customer said, in their words>
**Direction:** inbound | outbound | both   **Callers:** <country>   **Peak:** <N> concurrent, <N> CPS
**Who talks:** <AI agent on X | human in browser | IVR | notification>

### Architecture
<3-6 lines: number → Application/trunk → platform/server → transfer/recording. Name each Vobiz block.>

### Why this path
<2-3 bullets tied to the answers above, with the alternative you rejected and why>

### Before you build (compliance and account)
- KYC: <status / needed>
- Numbers: <type and series, who requests them, lead time>
- DLT / NDNC: <needed or not>
- Capacity: <concurrency and CPS to request>

### Build order
1. <step> - <docs page>
2. ...

### Read next
- <page> - <why>
- Skills to load for the build: `vobiz-...`

### Open points to confirm with Vobiz
- <anything not covered by a docs page>
```

If any line in "Open points" is empty because you guessed, go back and search the docs.

## Playbooks

The ten asks that come up most. Each is a starting answer; still run the interview.

**AI receptionist on a managed platform (Vapi, Retell, ElevenLabs).** Buy a DID → create an inbound trunk whose primary origination URI is the platform's SIP URI (the vendor integration page states the exact format to paste - copy it from there) → assign the number to the trunk → platform allow-lists the Vobiz gateway per [IP Whitelisting](https://www.vobiz.ai/docs/concepts/ip-whitelisting). Outbound from the same platform: outbound trunk + credentials, platform dials via `<trunk_id>.sip.vobiz.ai`. Pages: `/integrations/<vendor>-dashboard`, [Inbound AI agent guide](https://www.vobiz.ai/docs/guides/ai-voice-agent/inbound), [Outbound AI agent guide](https://www.vobiz.ai/docs/guides/ai-voice-agent/outbound). Skills: `vobiz-ai-voice-agents`, `vobiz-sip-trunking`.

**Self-hosted AI agent (Pipecat, custom).** Buy a DID → Application with `answer_url` → server returns `<Stream bidirectional="true" keepCallAlive="true">wss://…</Stream>` → attach number to the Application. Audio defaults to 8 kHz; match `start.mediaFormat`; the authoritative end-of-call signal is the `Event=Hangup` POST to `hangup_url`, not the socket closing. Pages: [Stream](https://www.vobiz.ai/docs/xml/stream), [Pipecat](https://www.vobiz.ai/docs/integrations/pipecat), [Gemini Live](https://www.vobiz.ai/docs/integrations/gemini-live), [WebSockets](https://www.vobiz.ai/docs/integrations/websockets). Skills: `vobiz-audio-streams`, `vobiz-applications-endpoints`.

**OpenAI Realtime.** SIP over TLS with SRTP: origination URI transport TLS, trunk `secure: true`. The symptom of a missed `secure` is a connected, billed, silent call. Page: [OpenAI Realtime](https://www.vobiz.ai/docs/integrations/openai-realtime).

**Cloud IVR with human fallback.** Application → `<Gather>` menu with `<Speak>` prompts → `<Dial>` to an endpoint, number, or SIP URI on the chosen option → fallback `<Speak>` + `<Hangup>`. Use `executionTimeout` on `<Gather>` (not `timeout`). Pages: [IVR example](https://www.vobiz.ai/docs/examples/vobiz-ivr-xml-python), [Cloud IVR](https://www.vobiz.ai/docs/solutions/cloud-ivr), [XML builder](https://www.vobiz.ai/docs/xml-builder). Skill: `vobiz-voice-xml`.

**Appointment reminders, OTP by voice, surveys.** Call API with `answer_url` → `<Speak>`/`<Gather>` → `hangup_url` for the result. Add `machine_detection` for voicemail. In India, transactional traffic belongs on a 160-series caller ID where the customer is eligible (see [Number series](https://www.vobiz.ai/docs/faq/number-series)), never on a promotional 140 number. Pages: [Make a call](https://www.vobiz.ai/docs/call/make-call), [Machine detection](https://www.vobiz.ai/docs/call/machine-detection), the `/examples` pages for reminders, OTP, and survey. Skills: `vobiz-voice-calls`, `vobiz-voice-xml`.

**Bulk outbound campaign.** Campaign Agent (answer/hangup URLs, reused) → caller-ID pool with rotation → CSV contacts → CPS, concurrency, daily window, retry budget → launch; drive it by API through the Campaign Manager endpoints under `/campaign-manager`. In India: 140 series for promotional, 160 for service, DLT first, NDNC consent on file. Pages: [Campaigns](https://www.vobiz.ai/docs/platform/campaigns/list), [Campaign manager guide](https://www.vobiz.ai/docs/best-practices/outbound-campaign-manager), [Automated outbound calling](https://www.vobiz.ai/docs/solutions/automated-outbound-calling).

**Browser or CRM calling for human agents.** Application for the call logic → Endpoint per agent (SIP username/password; a custom WebRTC client registers with those at `registrar.vobiz.ai`) → DID attached to the Application → XML `<Dial>` to the endpoint's `sip_uri` for inbound. For Zendesk, Freshdesk, HubSpot, Pipedrive, Zoho, Salesforce, ServiceNow, or ClickUp, use the ready integration page. Pages: [WebRTC setup](https://www.vobiz.ai/docs/integrations/webrtc-application-setup), [Contact centre](https://www.vobiz.ai/docs/solutions/contact-centre). Skill: `vobiz-applications-endpoints`.

**Connect a PBX, SBC, or existing carrier (BYOC).** Collect the customer's SIP signalling IPs and transport → trunk with IP ACL (static IPs) or credentials (dynamic IPs, NAT) → origination URIs with priority for failover and weight for load split → allow-list Vobiz per [IP Whitelisting](https://www.vobiz.ai/docs/concepts/ip-whitelisting). Every originating IP must be listed or calls fail with `403`. Pages: [BYOC](https://www.vobiz.ai/docs/concepts/bring-your-own-carrier), [SIP trunking](https://www.vobiz.ai/docs/concepts/sip-trunking), [3CX](https://www.vobiz.ai/docs/integrations/3cx). Skill: `vobiz-sip-trunking`.

**Multi-tenant platform.** Decide sub-account vs partner (2.6) → provision per customer with the parent credentials → `customer_use` sub-accounts or partner KYC sessions before calls → assign numbers per tenant → per-tenant CDRs for billing. Pages: [Sub-accounts vs partner accounts](https://www.vobiz.ai/docs/concepts/sub-accounts-vs-partner-accounts), [Partner flow](https://www.vobiz.ai/docs/partner/flow), [Sub-account onboarding](https://www.vobiz.ai/docs/sub-accounts/onboarding-flow). Skills: `vobiz-sub-accounts`, `vobiz-partner-api`.

**Number masking (marketplace, delivery).** Call API or inbound Application → `<Dial>` with the masked Vobiz number as caller ID → both parties see only the Vobiz number → CDR for the audit trail. Page: [Two-way number masking example](https://www.vobiz.ai/docs/examples/vobiz-two-way-number-masking-python), [Number masking](https://www.vobiz.ai/docs/solutions/number-masking).

## Hand off to the domain skill

Once the path is chosen, load exactly the skills the build needs:

| Build step | Skill |
|---|---|
| Buy, assign, or release numbers | `vobiz-phone-numbers` |
| Place and control calls, machine detection, transfer | `vobiz-voice-calls` |
| Write the XML flow | `vobiz-voice-xml` |
| WebSocket audio to an AI pipeline | `vobiz-audio-streams` |
| Trunks, credentials, IP ACL, origination URIs, BYOC | `vobiz-sip-trunking` |
| Applications and endpoints, WebRTC | `vobiz-applications-endpoints` |
| Connect a named AI platform | `vobiz-ai-voice-agents` |
| Call history, quality, billing data | `vobiz-cdr` |
| Tenants inside one account, KYC per tenant | `vobiz-sub-accounts` |
| Reseller accounts, balance transfer, capacity transfer | `vobiz-partner-api` |
| WhatsApp messaging | `vobiz-whatsapp` |
| Moving off Plivo | `vobiz-plivo-migration` |

## Cross-cutting pitfalls to put in every brief

- **Path casing is part of the contract.** `/Account/` for calls, numbers, trunks, CDRs; `/account/` for number-to-sub-account assignment; `/accounts/` for sub-account CRUD. Copy paths from the doc page.
- **A URL in XML must be fully qualified HTTPS** and return a `<Response>` document served as `application/xml` or `text/xml`; a non-2xx reply or invalid XML ends the call with hangup cause `7011` or `8011`. Set `fallback_answer_url` on the Application.
- **Trial numbers do not take inbound calls.** Plan KYC and a purchased number before the inbound demo.
- **India caller ID must be a Vobiz India number** on domestic routes; a non-Vobiz caller ID is processed best-effort and falls outside Vobiz support.
- **Paste a platform's SIP URI into a Vobiz origination URI in exactly the format the vendor integration page states** - copy it from there; a wrong format causes immediate disconnects. Use the trunk's exact `<id>.sip.vobiz.ai`, never a generic `sip.vobiz.ai`.
- **Trunk webhooks are one-way notifications.** Their response does not accept or reject a call, and they are not currently signed; verify by source IP via [IP Whitelisting](https://www.vobiz.ai/docs/concepts/ip-whitelisting#callbacks). Application callbacks carry HMAC signature headers when the callback URL has auth credentials configured - fail closed if an expected signature is absent; see [Validating callbacks](https://www.vobiz.ai/docs/concepts/validating-callbacks).
- **CDRs appear after the call ends.** For live state use the Call API with `status=live`, or trunk webhooks.
- **Capacity errors look like outages.** `429` or SIP `503` at peak is a concurrency or CPS ceiling, not a routing fault.
- **WhatsApp's first message to a new contact must be an approved template.**
- **Balance transfers and purchases are irreversible.** Show the account, amount, and currency and get a yes.

## When to search docs

- "Which AI platform should they use?" → `/integrations`, `/concepts/sip-vs-websockets`
- "Can they keep their numbers?" → `/concepts/bring-your-own-carrier`
- "What will this cost?" → `/resources/calculator`, `/concepts/sip-vs-websockets`
- "What number do they need in India?" → `/faq/number-series`, `/best-practices/140-160-acquisition`
- "Sub-account or partner?" → `/concepts/sub-accounts-vs-partner-accounts`
- "How do they get CPS or concurrency?" → `/faq/purchase-concurrency-cps`
- "Is there a worked example?" → `/examples`, `/solutions`
- "What does the industry do?" → `/solutions/<industry>` for healthcare, fintech, real estate, logistics, e-commerce