What it does
Zernio is a developer API that lets an app or an AI agent publish and act across marketing channels through one integration and one API key. It covers posting, scheduling, comments, DMs and analytics on 16 social networks, campaign management on seven ad platforms, WordPress and Shopify articles, and phone numbers that send WhatsApp, SMS and calls. It ships SDKs, a CLI and an MCP server so assistants such as Claude Code, Cursor or Codex can use it directly. Billing is per connected account, with the first two free. Zernio was previously called Late.
Official source 1 ↗ · Official source 2 ↗Features
- Unified social media API. One API posts, schedules, replies to comments and DMs, and reads analytics across 16 networks, including X, Instagram, TikTok, LinkedIn, Facebook, YouTube, Threads, Pinterest, Reddit, Bluesky, Telegram, Discord, Slack and Google Business Profile. Official source 1 ↗ · Official source 2 ↗
- Scheduling tools. Posts can be published immediately, scheduled in a given timezone or saved as drafts. Bulk CSV upload, queue slots and automatic first comments are also available. Official source 1 ↗ · Official source 2 ↗
- Advertising API. Creates campaigns, ad sets and creatives, changes budgets, pauses and resumes ads, and reads spend across Meta, Google, LinkedIn, TikTok, Pinterest, X and OpenAI Ads from one set of endpoints. Official source 1 ↗
- Phone numbers, WhatsApp, SMS and calls. Buy a number in a supported country, then send WhatsApp messages, SMS and calls from it. Replies land in one inbox, which suits voice agents and chatbots. Official source 1 ↗
- Inbox, comments and automations. Read and reply to DMs, comments and reviews, and set up comment-to-DM automations. The CLI also covers broadcasts, sequences and workflows. Official source 1 ↗ · Official source 2 ↗
- Blogs API. Create, edit, publish and delete articles on connected WordPress sites and Shopify stores. Official source 1 ↗
- Built for AI agents. The MCP server, a setup prompt for Claude Code, Cursor and Codex, and a CLI that prints JSON let assistants call Zernio directly. Real-time webhooks report post status, messages and comments. Official source 1 ↗ · Official source 2 ↗ · Official source 3 ↗
Pricing & free limits
No plans or seats; every feature is included on every account. The first 2 connected accounts are free with no credit card. After that, each connected account costs $6 a month (accounts 3–10), $3 (11–100) or $1 (101 and above). Messages, managed ads, phone numbers and calls are metered on top. Official source 1 ↗
The same platform with custom rates, available past 2,000 accounts. Includes SAML SSO, SCIM, audit logs and RBAC, a dedicated Slack channel with engineering, and SOC 2 and GDPR paperwork. Official source 1 ↗
Billing details
Phone numbers bought from Zernio carry their own monthly fee (for example $3.00 a month for a US local number); calls and SMS on them are metered separately. Official source 1 ↗
WhatsApp message fees are Meta's own rates. Meta bills them to your WhatsApp Business Account, and Zernio adds no markup. Official source 1 ↗
Managed ads are metered per active ad, and X API calls are passed through at X's own rates. Official source 1 ↗
Free access & limits
Two connected accounts are free without a card, except X, which needs a card because X bills every API call. The first 10,000 DMs sent a month are free. Official source 1 ↗ · Official source 2 ↗
Best for & limitations
Letting an AI agent or coding assistant publish, reply and report on social accounts through the MCP server or CLI. Official source 1 ↗
Building a SaaS product whose users connect their own social accounts, with one profile per user. Official source 1 ↗
Running a WhatsApp, SMS or voice-agent inbox on a number bought through Zernio. Official source 1 ↗
- Connected assistants get account-wide access. Approving an MCP connection lets the assistant call every Zernio tool, including running ad campaigns that spend your budget. Data it requests is sent to the assistant's provider, under that provider's own policy. Official source 1 ↗
- Total cost depends on several meters. Beyond per-account fees, bills can include message, ad, phone-number, call and SMS charges, X API pass-through costs, and Meta's WhatsApp fees billed separately by Meta. Official source 1 ↗
- WhatsApp calling limits on US numbers. Meta blocks business-initiated WhatsApp calls from US numbers, so outbound calling on a US number is not available; customers can still call in. Official source 1 ↗
- Snapchat in closed beta. Snapchat is listed as a closed-beta platform in the quickstart. Official source 1 ↗
- Developer-oriented. Setup is API-key and code based (SDKs, CLI, MCP). The site counts 16 networks on the homepage and 17 on the features page. Official source 1 ↗ · Official source 2 ↗
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