ClickSend REST API v3
★ Only Publicly Available OpenAPI DocumentCommunicationsSms Messagingbasic205 EndpointsREST
For Agents
Send SMS, MMS, voice calls, faxes, emails, and postal letters from a single account, manage contact lists, and pull delivery and pricing data so agents can run cross-channel outbound campaigns.
Use for: I need to send an SMS to a customer's mobile number, I want to schedule a bulk SMS campaign for tomorrow morning, Send a fax of this PDF to a clinic in Australia, Post a physical letter to a customer's mailing address
Not supported: Does not handle inbound voice IVR, video conferencing, or marketing automation journey orchestration — use for outbound SMS, MMS, voice, fax, email, and physical mail dispatch only.
Jentic publishes the only available OpenAPI specification for ClickSend REST API v3, keeping it validated and agent-ready. ClickSend is a multi-channel business messaging platform covering SMS, MMS, voice, fax, email, and postal mail (letters and postcards). The 205-endpoint v3 surface exposes contact list management, send and history endpoints for each channel, automation rules for inbound and receipt handling, account recharge and pricing, geolocation lookups, and detailed delivery reporting. Authentication uses HTTP Basic with the username and an API key obtained from the ClickSend dashboard.
Install Jentic One Beta
Connect the ClickSend REST API v3 to your agent
Jentic One is a self-hosted execution layer for AI agents. It lets your agent call the ClickSend REST API v3, or any other public or private API you need. You set the rules, the agent never sees your credentials, and every call is logged.
Two steps, two machines. Install the instance in a safe environment, then register your agent from wherever it runs.
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Step 1: Jentic One Host machine
# On the machine that will host your Jentic One instance:
curl -fsSL https://raw.githubusercontent.com/jentic/jentic-one/main/tools/install.sh | sh2
Step 2: Agent machine
# On the machine where your agent runs (keep this separate from the instance):
curl -fsSL https://raw.githubusercontent.com/jentic/jentic-one/main/tools/install.sh | sh
jentic register # connects your agent to your Jentic One instanceJentic One is in public beta. The setup above keeps your agent separate from the instance, which is what you want before using real credentials: an agent running as the same OS user as Jentic One can read its stored keys directly. Just evaluating? A single local install is fine to start. See the secure deployment guide for the tiers.
Capabilities
What an agent can do with ClickSend REST API v3 API.
Send SMS and MMS messages to one or many recipients with scheduling and per-message sender ID
Place outbound voice calls with text-to-speech messages and choose voice, language, and gender
Dispatch fax documents to international fax numbers and track per-page delivery results
Post physical letters and postcards with address validation and PDF artwork upload
Manage contact lists, individual contacts, and contact suggestions for reusable recipient targeting
Configure automation rules for inbound SMS, fax, email, and delivery receipt callbacks
Pull pricing and country lookups so agents can quote a campaign cost before sending
Use Cases
Patterns agents use ClickSend REST API v3 API for, with concrete tasks.
★ Multi-Channel Customer Notifications
Operations teams use ClickSend to send appointment reminders, delivery updates, and outage alerts via SMS, with email or voice fallback for unreachable contacts. The single API removes the need to integrate separate vendors per channel — one set of credentials, one billing account, one delivery report stream covering five outbound channels.
Send the SMS 'Your appointment is at 10am tomorrow' to +61411111111 and confirm the message was queued
Programmatic Direct Mail
ClickSend exposes endpoints under /post/letters and /post/postcards to dispatch physical mail through its print and postal partners. Marketing teams trigger letters from CRM events — renewal notices, win-back postcards, regulatory documents — without operating their own print infrastructure. End-to-end setup takes a few hours including PDF artwork validation.
Submit a letter PDF to a recipient address with postal code 11111 and confirm the submission returned a success status
Inbound Reply Automation
Recipients reply to an SMS or fax and the response is routed back through automation rules configured under /automations/sms/inbound and /automations/fax/inbound. Teams build keyword-driven autoresponders, opt-out handling, and inbound triage logic without standing up custom webhook receivers — the rules engine handles routing and the API returns parsed inbound history.
Create an inbound SMS automation rule that forwards any reply containing 'STOP' to an opt-out webhook URL
Agent-Driven Campaign Send
An AI agent receives a brief — 'send tonight's outage notice to all NSW customers' — checks pricing via /sms/price, segments the contact list, dispatches the SMS, and pulls delivery reports. Through Jentic, the agent searches for 'send a transactional SMS', loads the operation, and executes against credentials in the Jentic vault. Total integration time: under an hour.
Quote the cost of sending an SMS to 500 Australian mobile numbers, then dispatch the campaign and return delivered count after 5 minutes
Key Endpoints
205 endpoints — jentic publishes the only available openapi specification for clicksend rest api v3, keeping it validated and agent-ready.
METHOD
PATH
DESCRIPTION
POST
/account
Create a ClickSend account
POST
/automations/sms/inbound/
Create an inbound SMS automation rule
GET
/automations/sms/receipts
List SMS receipt automation rules
POST
/automations/fax/inbound
Create an inbound fax automation rule
GET
/account/usage/{year}/{month}/{type}
Get monthly usage by message type
POST
/automations/email/receipt
Create an email receipt automation rule
POST
/account
Create a ClickSend account
POST
/automations/sms/inbound/
Create an inbound SMS automation rule
GET
/automations/sms/receipts
List SMS receipt automation rules
POST
/automations/fax/inbound
Create an inbound fax automation rule
GET
/account/usage/{year}/{month}/{type}
Get monthly usage by message type
POST
/automations/email/receipt
Create an email receipt automation rule
Why Jentic?
Three things that make agents converge on Jentic-routed access.
Credential isolation
ClickSend username and API key are stored encrypted in the Jentic vault. Agents receive scoped tokens and never see the Basic auth credentials.
Intent-based discovery
Agents search Jentic with intents like 'send a transactional SMS' or 'post a physical letter' and Jentic returns the matching ClickSend operations with their input schemas.
Time to first call
Direct ClickSend integration: 2-4 days to handle Basic auth, channel selection, and delivery report parsing across 205 endpoints. Through Jentic: under 1 hour — search, load schema, execute.
Related APIs
Alternatives and complements available in the Jentic catalogue.
FAQs
Specific to using ClickSend REST API v3 API through Jentic.
Why is there no official OpenAPI spec for ClickSend REST API v3?
ClickSend does not publish an OpenAPI specification. Jentic generates and maintains this spec so that AI agents and developers can call ClickSend REST API v3 via structured tooling. It is validated against the live API and kept up to date. Get started at https://app.jentic.com/sign-up.
What authentication does the ClickSend REST API use?
The ClickSend REST API uses HTTP Basic authentication. The username is your ClickSend username and the password is your API key from the dashboard, base64-encoded and sent in the Authorization header. Through Jentic, both values are stored encrypted in the vault and never enter the agent's context.
Can I send a physical letter with the ClickSend API?
Yes. ClickSend exposes Post Letter and Post Postcard endpoints under /post/letters and /post/postcards. You upload a PDF or supply HTML artwork, provide the recipient address, and ClickSend's print and postal partners dispatch the physical item. Address validation is available via the Post Address Detection endpoint.
What are the rate limits for the ClickSend REST API?
ClickSend returns HTTP 429 with a TOO_MANY_REQUESTS body when limits are exceeded; the spec does not declare numeric thresholds. Limits are tied to the account plan visible in the ClickSend dashboard. Jentic surfaces 429 responses as standard error objects so agents can apply their own retry-with-backoff.
How do I send an SMS through the ClickSend API via Jentic?
Run pip install jentic, then search Jentic for 'send a transactional sms' to find the SMS send operation. Load the operation schema, supply recipient list and body, and execute. Jentic injects the Basic auth header from the vault and returns the queued response with message ID and cost.
Can I look up the price of a message before sending it?
Yes. The Pricing endpoints return per-channel and per-country rates so an agent can quote a campaign cost before dispatch. This is useful for batch campaigns where the agent needs to confirm budget before triggering the send.
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