Inkbox gives AI agents email, a phone number, shared-pool iMessage, and a public tunnel URL; Dial gives them a real phone identity that calls, texts worldwide, WhatsApps, and iMessages on its own number. An honest comparison.
TL;DR
Inkbox (inkbox.ai, YC S26) shares Dial's agent-native thesis and extends it sideways: every agent identity gets an email inbox, a public tunnel URL, and a credential vault alongside phone and iMessage — primitives Dial doesn't offer. Where it thins out is exactly where agents do outbound real-world work: iMessage rides a shared pool the agent can't initiate on (the human must text connect first, with 2–15 unique recipients per org per month by plan), voice means hosting your own agent behind a live WebSocket, numbers are US-only, and there's no WhatsApp and no MCP server. Dial gives the agent numbers of its own — agent-initiated iMessage, fully hosted AI voice, SMS to 200+ countries, WhatsApp — one identity built to reach out, not just be reached.
| Dial | Inkbox | |
|---|---|---|
| What it is | Communication stack for AI agents — number, voice, SMS, WhatsApp, iMessage in one API | Identity layer for AI agents — email, phone, shared-pool iMessage, tunnel, vault |
| Pricing model | Usage-based, published — $3/mo numbers, $0.02 SMS, $0.13–0.22/min voice, $5 free credit | Subscriptions — $0 / $10 / $25 per month with bundled allowances that don't roll over |
| Phone numbers | $3/mo each, self-serve · US, Canadian, and international | Bundled — 1 phone-enabled identity at $10/mo, 3 at $25/mo · US-only · none on the free tier |
| Voice calls | Hosted AI voice $0.22/min, or your LLM over WebSocket $0.13/min — no infrastructure to run | $0.03/min raw (30 min bundled) — you host the agent behind a live WebSocket endpoint |
| iMessage | Dedicated $250/mo number — agent-initiated cold outbound, automatic RCS/SMS fallback | Shared pool — human must text connect first; 2–15 unique recipients per org/mo by plan; 100 msgs/identity per 24h; no groups |
| SMS reach | $0.02/msg US · 200+ countries in 7 tiers | 300/mo bundled per phone identity, then $0.03 · shared campaign caps sends at 100 recipients/24h (own 10DLC: $20/mo) |
| Included — same identity, 180+ countries | Not offered | |
| Not offered | First-class — inbox, threading, search, custom domains, open tracking | |
| Tunnel & vault | Not offered | Public HTTPS/WebSocket/TCP URL per agent + shared contacts, notes, encrypted credential vault |
| MCP server | Remote MCP with OAuth — 99.9% 30-day uptime on Smithery (July 2026) | None — SDKs, CLI, installable skill, and per-runtime plugins |
| Agent self-provisioning | skills.md, CLI, or MCP — a message-ready number in ~10 seconds | Yes — API self-signup with graduated limits; human approves via email code |
| Free tier | $5 credit, no credit card — enough for a real number and live traffic | $0 plan — 3 identities with email and limited iMessage, no phone numbers |
Based on each product's public documentation and published pricing as of July 8, 2026. Spotted something out of date? Email [email protected] and we'll fix it.
Inkbox (inkbox.ai) is a Y Combinator S26 startup building "the identity layer for AI agents": each identity gets a real email inbox (with threading, search, and custom domains), an optional US phone number for calls and SMS/MMS, shared-pool iMessage, a persistent public tunnel URL, and org-wide contacts, notes, and an encrypted credential vault. Pricing is subscription tiers — free (3 identities, no phone), $10/month (1 phone-enabled identity), $25/month (3 phone-enabled) — with 300 SMS and 30 call minutes bundled per phone identity, then $0.03 per message or minute. Voice streams over a WebSocket to an agent you host; iMessage is receive-first (humans text connect @agent to start) with per-plan unique-recipient caps. Python/TypeScript SDKs, a CLI, an installable skill, and Claude Code/Codex/OpenClaw/Hermes plugins; no WhatsApp and no MCP server.
Dial is the communication stack for AI agents: provision a real phone number in about 10 seconds and your agent can place and receive voice calls, send and receive SMS in 200+ countries, message on WhatsApp, and reach iMessage with automatic RCS/SMS fallback — all through one REST API, CLI, or MCP server. Pricing is all-in: $3/month per number pay-as-you-go (or $20/month flat-rate with US calls and SMS included), $0.13/min for calls with your own LLM, $0.22/min fully managed. $5 free credit, no credit card.
Inkbox is thinking about the same future Dial is — agents with persistent, real-world identities — and it extends that identity in directions Dial doesn't. Email is genuinely first-class: threading, search, reply-all, open tracking, custom domains. Every agent gets a persistent public tunnel URL (HTTPS, WebSocket, or TCP), which is a clever primitive for reaching an agent from anywhere. Org-wide contacts, notes, and a zero-knowledge credential vault round out the identity. The self-signup flow is thoughtfully designed too: an agent can bootstrap an account by API before any human account exists, with graduated sending limits until a human approves.
If what your agent needs first is an email address and an internet address, Inkbox is the more interesting product — full stop.
The iMessage architectures differ fundamentally, and Inkbox's docs are upfront about theirs: identities don't get an iMessage number of their own — messages route through Inkbox's shared pool, a conversation only starts after the human texts connect @agent-name first, and sending is capped at 100 messages per identity per rolling 24 hours with no group chats. Plan limits cap reach further: 2 unique iMessage recipients per org per month on the free plan, 5 at $10/month, 15 at $25/month. Dedicated iMessage infrastructure exists only as a custom Enterprise conversation.
Dial's iMessage is the agent's own dedicated number ($250/month, messages free): it can initiate — cold outbound included — with automatic RCS/SMS fallback for Android recipients. If iMessage is a support inbox for a handful of known users, Inkbox's pool is fine; if your agent texts customers first, the recipient caps are the whole ballgame.
Inkbox's $0.03/minute is real and it's cheap — but read what it buys: raw call streaming over a WebSocket (with optional managed STT/TTS) to an agent *you* host at a live, reachable endpoint. The tunnel product exists partly to make that hosting problem tractable. There is no hosted voice-agent mode: if your process is down, your phone is down.
Dial offers both shapes. Managed mode ($0.22/min) is a complete voice agent on the number — model, speech, turn-taking, telephony — with zero infrastructure on your side. Self-hosted mode ($0.13/min) is the same architecture as Inkbox's, except Dial still runs the telephony, speech, and turn-taking and hands your LLM clean text. Comparing $0.03 to $0.22 head-on isn't apples-to-apples — the honest statement is: Inkbox sells you cheaper raw minutes and the hosting problem; Dial sells you a working phone.
Inkbox prices like a SaaS: $0, $10, or $25 a month with bundled allowances (300 SMS + 30 minutes per phone-enabled identity) that don't roll over, and no phone numbers at all on the free tier. For a hobby agent that texts a few times a day, $10/month all-in is a genuinely good deal.
Dial prices like infrastructure: $5 of free credit provisions a real number and carries live traffic in the first minute, then usage rates published for every capability — $3/month numbers, $0.02 SMS, $0.13–0.22/minute voice, with a $20/month flat-rate envelope when an agent runs hot. At production volume the comparison inverts: Inkbox's Developer plan tops out at 3 phone-enabled identities and 15 iMessage recipients a month before you're in a custom Enterprise conversation, while Dial's published rates just keep scaling — 200+ SMS countries, WhatsApp, and as many numbers as your agents need.
They overlap on phone and iMessage for AI agents, and differ at the edges: Inkbox adds email, a public tunnel URL, and a credential vault, while Dial adds hosted AI voice, WhatsApp, international SMS, agent-initiated iMessage on a dedicated number, and an MCP server. Agents that need to reach out across channels fit Dial; agents that need an email address and an internet address fit Inkbox.
No — per Inkbox's docs, iMessage routes through a shared number pool, the human must text connect @agent-name before a conversation exists, sending is capped at 100 messages per identity per 24 hours, and plans cap unique recipients at 2–15 per org per month. Dial's dedicated iMessage numbers ($250/month, messages free) support agent-initiated cold outbound with automatic RCS/SMS fallback.
The raw minute is — $0.03 vs $0.13–0.22 — but it buys different things. Inkbox streams the call over a WebSocket to an agent you host at a live endpoint; there's no hosted voice mode. Dial's $0.22/min is a complete hosted voice agent, and its $0.13/min WebSocket mode still includes telephony, speech, and turn-taking handled for you. If you already run agent infrastructure 24/7, Inkbox's minutes are cheaper; if you want a phone that just works, Dial is the complete version.
Neither, as of July 2026 — there's no WhatsApp anywhere in Inkbox's product or docs, and no MCP server (its agent surface is SDKs, a CLI, an installable skill, and per-runtime plugins). Dial includes WhatsApp in 180+ countries and runs a remote MCP server with OAuth, registry-monitored at 99.9% 30-day uptime on Smithery.
For a small agent that mostly receives, Inkbox's $10–25 bundles are hard to beat. For agents that initiate and scale, Dial usually wins: the free $5 credit includes a real number (Inkbox's free tier has none), SMS is $0.02 vs $0.03 overage, iMessage isn't capped at 15 recipients a month, and there's a $20/month flat-rate envelope — with no Enterprise sales call required to grow.
Voice, SMS, WhatsApp, and iMessage through one API. $5 free credit, no credit card required.