# A2P Messaging API Send messages straight from your code — built for developers and AI agents. A simple REST API (and SMPP) with delivery tracking and webhooks: SMS today, with RCS and WhatsApp coming soon. No audience to manage: bring your recipients and send. **Language:** en **Audience:** developer **TLDR:** The A2P Messaging API sends messages from your code: SMS today, RCS and WhatsApp coming soon. One at a time (POST /sms) or in batches (POST /sms/bulk), with DLRs pushed to your webhook, two-way inbound, message history, HLR lookups, balance and price profiles, over HTTP or SMPP. It is the Transactional API under its newer name: same endpoints, tokens and URLs. Use it when you manage your own recipient list; if Instasent should own the audience, use the platform. **Search keywords:** a2p messaging api, a2p, transactional api, sms api, smpp, bulk sms, dlr, hlr lookup **Docs index (every page):** https://staging-instasent-docs-nextjs.oscar-284.workers.dev/llms.txt **This zone's index:** https://staging-instasent-docs-nextjs.oscar-284.workers.dev/a2p-messaging-api/llms-full.txt **This page:** https://staging-instasent-docs-nextjs.oscar-284.workers.dev/a2p-messaging-api/overview/ (HTML) · https://staging-instasent-docs-nextjs.oscar-284.workers.dev/a2p-messaging-api/overview.md (Markdown) > **Note**: **The Transactional API and the A2P Messaging API are the same API** — and, > before both, the SMS API. Same endpoints, same tokens, same URLs, nothing to > migrate: if your integration calls the Transactional API, it is already > calling this. The dashboard uses the newer name, so what you create there is > an *A2P Messaging API* token or project. > > It is also the **evolution of the [Legacy API](/a2p-messaging-api/legacy/overview)**: > the same endpoint surface, modernised with DLR webhooks, per-project tokens, > SMPP and the `api_sms` token model. If you are about to write new code, write > it against this API. The A2P Messaging API is how your code sends messages through Instasent. It connects your application to carrier networks, delivering to handsets in 200+ countries, and covers everything around the send: single or batched sending, DLRs and inbound, message history, HLR lookups, price profiles and account balance. Today it sends **SMS**; **RCS and WhatsApp are coming soon**. Two transports expose the same underlying pipeline. Pick the one that fits your stack — most teams start with HTTP and only move to SMPP when volume or session-state requirements justify it. - [HTTP (REST)](/a2p-messaging-api/http/quickstart) - JSON over HTTPS. Best for application servers, serverless functions and anything that already speaks REST. Webhook-based DLRs. - [SMPP](/a2p-messaging-api/smpp/integration) - Persistent TCP sessions, binary protocol. Best for wholesale SMS and high-throughput platforms (messaging providers, aggregators) that already operate an SMPP stack. ## What you can do - **Send SMS, one at a time** — `POST /sms` for triggered traffic (OTPs, alerts, receipts, notifications). - **Send SMS in bulk** — `POST /sms/bulk` takes a collection of messages in a single request. This is the endpoint for API-driven campaigns, marketing fan-outs and any high-volume dispatch. Customers including marketing agencies run entire campaigns on top of it. - **Receive delivery reports** (DLRs) as carriers report status back through the chain, pushed to your webhook in real time. - **Accept inbound messages** when the account has two-way enabled. - **Query message history** and per-message status — `GET /sms`, `GET /sms/{id}`. - **Run HLR / number lookups** — `POST /lookup`, `GET /lookup/{id}` and `GET /lookup` to check handset presence and routing before sending. - **Read account balance** — `GET /organization/account`. - **Read price profiles** — `GET /sms/price-profile/me/countries` and `GET /lookup/price-profile/me/countries` for per-country pricing. ## When to use this API Reach for A2P Messaging whenever your code needs to send — one message or many — without asking Instasent to manage the recipient audience. Typical workloads: - **User-triggered messages** — OTPs, password resets, receipts, shipping notifications. One message per event, delivered in seconds, via `POST /sms`. - **API-driven campaigns and bulk dispatch** — marketing sends, notification fan-outs, anything that fires many messages in one go. Use `POST /sms/bulk`. - **Wholesale SMS over SMPP** — aggregators, messaging platforms and resellers pushing their own traffic through Instasent. [SMPP](/a2p-messaging-api/smpp/integration) gives carrier-grade throughput over persistent sessions; HTTP also works at moderate rates. - **Pre-send validation and pricing** — HLR lookup and price profiles to route and cost-check before dispatch. If you need Instasent to own the audience, personalization, segmentation and attribution, use the [Product API](/platform-api/product-api/guide) instead — it delegates delivery to this one but adds the customer-data layer on top. The A2P Messaging API is the right pick when the caller already manages its recipient list and just needs to send. ## What to read next - [HTTP Quickstart](/a2p-messaging-api/http/quickstart) - Send your first SMS over REST in under five minutes. - [Bulk sending](/a2p-messaging-api/http/bulk) - Up to 100 messages per request, queue-based dispatch, the endpoint for API-driven campaigns. - [HTTP Authentication](/a2p-messaging-api/http/authentication) - Token types, header vs. query string, rotation. - [Receiving DLRs](/a2p-messaging-api/http/dlrs) - Webhook payload, status list, two-way inbound. - [Full API Reference](/a2p-messaging-api/http/reference) - Every endpoint, every parameter. --- This is one page of the Instasent documentation. For the complete machine-readable index of every guide and API reference, fetch https://staging-instasent-docs-nextjs.oscar-284.workers.dev/llms.txt — start there for full context.