ClickSend website screenshot

ClickSend

ClickSend is a cloud communications company providing a single REST API for business messaging across SMS, MMS, voice / text-to-speech, transactional email, and physical post - letters and postcards printed and mailed globally. The v3 API (rest.clicksend.com/v3) uses HTTP Basic authentication with a username and API key and covers sending, delivery receipts, inbound handling, contacts and lists, and account balance.

ClickSend publishes 10 APIs on the APIs.io network, including Account API, Contact API, ContactList API, and 7 more. Tagged areas include Communications, SMS, MMS, Voice, and Email.

ClickSend’s developer surface includes authentication, documentation, engineering blog, and 9 more developer resources.

🌐 Visit website 📡 Source on GitHub
37.5/100 thin ▬ flat Agent 22/100 agent aware Full breakdown ↓
scored 2026-08-24 · rubric v0.13.0
AccessPaidSelf serve
10 APIs
CommunicationsSMSMMSVoiceEmailMessagingCPaaS

Kin Score

Kin Score Kin Score How this is scored →
scored 2026-08-24 · rubric v0.13.0
Composite quality — 37.5/100 · thin
Contract Quality 10.4 / 21
Developer Ergonomics 4.0 / 17
Access Clarity 8.1 / 17
Operational Transparency 3.8 / 11
Contract Governance 0.0 / 10
Discoverability 6.3 / 9
Regulatory Posture 3.5 / 15
Agent readiness — 22/100 · agent aware
Machine-Readable Contract 18 / 18
Agentic Access Contract 10 / 10
Documented Reversibility 6 / 6
MCP Server 0 / 12
Machine-Readable Auth 10 / 10
Idempotency 0 / 9
Stable Error Semantics 0 / 8
Request/Response Examples 0 / 7
Rate-Limit Signaling 7 / 7
Typed Event Surface 0 / 6
Agent Skills 0 / 5
Well-Known Catalog 0 / 4
Consent & Bot Identity 0 / 3
A2A Agent Card 0 / 8
Dry-Run / Simulate Mode 0 / 4
Regulatory Posture applies to this provider. Its tags matched the Telecommunications regime, so Regulatory Posture carries 15 points of the composite. If this regime is wrong for your business, say so on your provider repo — the applicability map is public and we will correct it.
The six quality facets above are damped to 85 points between them, because the conditional facet above carries the other 15. That is why each facet's contribution is shown against a damped maximum: raising a quality facet moves the composite by 85% of its nominal weight, not 100%. The full arithmetic is at apis.io/rating/.
Improve this rating by publishing the missing artifacts — every area above can be raised, and the full rubric is at apis.io/rating/. This rating is computed from github.com/api-evangelist/clicksend: open an issue to ask a question, or submit a pull request to add artifacts. Want it done for you? Prioritized profiling — $2,500 →

APIs 10

Individual APIs this provider publishes, each with its own machine-readable definition.

ClickSend Account API

Account details, usage, and balance.

ClickSend Contact API

Manage contacts.

ClickSend ContactList API

Manage contact lists.

ClickSend Email API

Send and view transactional email.

ClickSend MMS API

Send and view MMS messages.

ClickSend Post Letter API

Print and mail physical letters.

ClickSend Post Postcard API

Print and mail physical postcards.

ClickSend Receipts API

Delivery receipts, inbound messages, and automations.

ClickSend SMS API

Send and view SMS messages.

ClickSend Voice API

Send and view voice (text-to-speech) messages.

Scroll for all 10

Open Collections 12

Open, tool-agnostic API collections (OpenAPI-derived and Bruno).

API Collection

OPEN COLLECTION

ClickSend v3 Account API

OPEN COLLECTION

ClickSend v3 Account Contact API

OPEN COLLECTION

ClickSend v3 Account ContactList API

OPEN COLLECTION

ClickSend v3 Account Email API

OPEN COLLECTION

ClickSend v3 Account MMS API

OPEN COLLECTION

ClickSend v3 Account Post Letter API

OPEN COLLECTION

ClickSend v3 Account Post Postcard API

OPEN COLLECTION

ClickSend v3 Account Receipts API

OPEN COLLECTION

ClickSend v3 Account SMS API

OPEN COLLECTION

ClickSend v3 Account Voice API

OPEN COLLECTION

ClickSend v3 API

OPEN COLLECTION

Scroll for all 12

Pricing Plans 1

Published pricing tiers and plan structures.

Clicksend Plans Pricing

3 plans

PLANS

Rate Limits 1

Documented rate limits and quota policies.

Clicksend Rate Limits

3 limits

RATE LIMITS

FinOps 1

Cost, billing, and metering signals for API financial operations.

Clicksend Finops

FINOPS

Security Posture 3

Authentication, domain security, vulnerability disclosure, and trust-center signals.

Clicksend Authentication

http · 1 scheme

SECURITY

Clicksend Domain Security

TLSv1.2 · DMARC

SECURITY

Clicksend Trust Center

SOC 2, ISO 27001, PCI DSS, HIPAA, GDPR

SECURITY

Agentic Access 1

Recommended x-agentic-access execution contracts for AI agents.

Clicksend Agentic Access

42 operations · 22 acting

42 operations · 22 acting

AGENTIC

Resources

Documentation 1

Reference material describing how the API behaves

Documentation
Documentation

Agent Surfaces 1

MCP servers, agent skills, and machine-readable catalogs

AgenticAccess
AgenticAccess

Build 1

SDKs, sample code, and the tooling you integrate with

GitHubOrganization
GitHubOrganization

Access & Security 3

Authentication, authorization, and security posture

TrustCenter
TrustCenter
 DomainSecurity
DomainSecurity
 Authentication
Authentication

Operate 1

Status, limits, changes, and where to get help

RateLimits
RateLimits

Commercial 2

Pricing, plans, and the legal terms of use

Plans
Plans
 FinOps
FinOps

Company 3

The organization behind the API

LinkedIn
LinkedIn
 Website
Website
 Blog
Blog

Source (apis.yml)

apis.yml Raw ↑ 
aid: clicksend
url: https://raw.githubusercontent.com/api-evangelist/clicksend/refs/heads/main/apis.yml
name: ClickSend
kind: company
description: ClickSend is a cloud communications company providing a single REST API for business messaging across SMS, MMS,
  voice / text-to-speech, transactional email, and physical post - letters and postcards printed and mailed globally. The
  v3 API (rest.clicksend.com/v3) uses HTTP Basic authentication with a username and API key and covers sending, delivery receipts,
  inbound handling, contacts and lists, and account balance.
accessModel:
  pricing: paid
  onboarding: self-serve
  trial: false
  try_now: false
  public: false
  label: Paid · Self-serve signup
  confidence: high
  source:
  - plans
  - authentication
  generated: '2026-07-22'
  method: derived
image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/icons/clicksend.png
tags:
- Communications
- SMS
- MMS
- Voice
- Email
- Messaging
- CPaaS
tags_raw:
- Communications
- SMS
- MMS
- Voice
- Email
- Post
- Messaging
- CPaaS
created: '2026-07-01'
modified: '2026-07-01'
specificationVersion: '0.23'
apis:
- aid: clicksend:clicksend-account-api
  name: ClickSend Account API
  description: Account details, usage, and balance.
  humanURL: https://developers.clicksend.com/docs/messaging/sms
  baseURL: https://rest.clicksend.com/v3
  tags:
  - Account
  properties:
  - type: OpenAPI
    url: openapi/clicksend-account-api-openapi.yml
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/sms
  - type: APIReference
    url: https://developers.clicksend.com/docs/rest/v3/
  - type: PostmanCollection
    url: collections/clicksend.postman_collection.json
  - type: OpenCollection
    url: collections/clicksend.opencollection.json
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/mms
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/voice-messaging
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/email
  - type: Documentation
    url: https://developers.clicksend.com/docs/post/letters
  - type: Documentation
    url: https://developers.clicksend.com/docs/post/postcards
  - type: Documentation
    url: https://developers.clicksend.com/docs/contacts
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/sms/receive-sms
  - type: Documentation
    url: https://developers.clicksend.com/docs/account
- aid: clicksend:clicksend-contact-api
  name: ClickSend Contact API
  description: Manage contacts.
  humanURL: https://developers.clicksend.com/docs/messaging/sms
  baseURL: https://rest.clicksend.com/v3
  tags:
  - Contact
  properties:
  - type: OpenAPI
    url: openapi/clicksend-contact-api-openapi.yml
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/sms
  - type: APIReference
    url: https://developers.clicksend.com/docs/rest/v3/
  - type: PostmanCollection
    url: collections/clicksend.postman_collection.json
  - type: OpenCollection
    url: collections/clicksend.opencollection.json
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/mms
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/voice-messaging
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/email
  - type: Documentation
    url: https://developers.clicksend.com/docs/post/letters
  - type: Documentation
    url: https://developers.clicksend.com/docs/post/postcards
  - type: Documentation
    url: https://developers.clicksend.com/docs/contacts
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/sms/receive-sms
  - type: Documentation
    url: https://developers.clicksend.com/docs/account
- aid: clicksend:clicksend-contactlist-api
  name: ClickSend ContactList API
  description: Manage contact lists.
  humanURL: https://developers.clicksend.com/docs/messaging/sms
  baseURL: https://rest.clicksend.com/v3
  tags:
  - ContactList
  properties:
  - type: OpenAPI
    url: openapi/clicksend-contactlist-api-openapi.yml
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/sms
  - type: APIReference
    url: https://developers.clicksend.com/docs/rest/v3/
  - type: PostmanCollection
    url: collections/clicksend.postman_collection.json
  - type: OpenCollection
    url: collections/clicksend.opencollection.json
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/mms
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/voice-messaging
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/email
  - type: Documentation
    url: https://developers.clicksend.com/docs/post/letters
  - type: Documentation
    url: https://developers.clicksend.com/docs/post/postcards
  - type: Documentation
    url: https://developers.clicksend.com/docs/contacts
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/sms/receive-sms
  - type: Documentation
    url: https://developers.clicksend.com/docs/account
- aid: clicksend:clicksend-email-api
  name: ClickSend Email API
  description: Send and view transactional email.
  humanURL: https://developers.clicksend.com/docs/messaging/sms
  baseURL: https://rest.clicksend.com/v3
  tags:
  - Email
  properties:
  - type: OpenAPI
    url: openapi/clicksend-email-api-openapi.yml
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/sms
  - type: APIReference
    url: https://developers.clicksend.com/docs/rest/v3/
  - type: PostmanCollection
    url: collections/clicksend.postman_collection.json
  - type: OpenCollection
    url: collections/clicksend.opencollection.json
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/mms
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/voice-messaging
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/email
  - type: Documentation
    url: https://developers.clicksend.com/docs/post/letters
  - type: Documentation
    url: https://developers.clicksend.com/docs/post/postcards
  - type: Documentation
    url: https://developers.clicksend.com/docs/contacts
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/sms/receive-sms
  - type: Documentation
    url: https://developers.clicksend.com/docs/account
- aid: clicksend:clicksend-mms-api
  name: ClickSend MMS API
  description: Send and view MMS messages.
  humanURL: https://developers.clicksend.com/docs/messaging/sms
  baseURL: https://rest.clicksend.com/v3
  tags:
  - MMS
  properties:
  - type: OpenAPI
    url: openapi/clicksend-mms-api-openapi.yml
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/sms
  - type: APIReference
    url: https://developers.clicksend.com/docs/rest/v3/
  - type: PostmanCollection
    url: collections/clicksend.postman_collection.json
  - type: OpenCollection
    url: collections/clicksend.opencollection.json
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/mms
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/voice-messaging
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/email
  - type: Documentation
    url: https://developers.clicksend.com/docs/post/letters
  - type: Documentation
    url: https://developers.clicksend.com/docs/post/postcards
  - type: Documentation
    url: https://developers.clicksend.com/docs/contacts
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/sms/receive-sms
  - type: Documentation
    url: https://developers.clicksend.com/docs/account
- aid: clicksend:clicksend-post-letter-api
  name: ClickSend Post Letter API
  description: Print and mail physical letters.
  humanURL: https://developers.clicksend.com/docs/messaging/sms
  baseURL: https://rest.clicksend.com/v3
  tags:
  - Post Letter
  properties:
  - type: OpenAPI
    url: openapi/clicksend-post-letter-api-openapi.yml
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/sms
  - type: APIReference
    url: https://developers.clicksend.com/docs/rest/v3/
  - type: PostmanCollection
    url: collections/clicksend.postman_collection.json
  - type: OpenCollection
    url: collections/clicksend.opencollection.json
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/mms
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/voice-messaging
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/email
  - type: Documentation
    url: https://developers.clicksend.com/docs/post/letters
  - type: Documentation
    url: https://developers.clicksend.com/docs/post/postcards
  - type: Documentation
    url: https://developers.clicksend.com/docs/contacts
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/sms/receive-sms
  - type: Documentation
    url: https://developers.clicksend.com/docs/account
- aid: clicksend:clicksend-post-postcard-api
  name: ClickSend Post Postcard API
  description: Print and mail physical postcards.
  humanURL: https://developers.clicksend.com/docs/messaging/sms
  baseURL: https://rest.clicksend.com/v3
  tags:
  - Post Postcard
  properties:
  - type: OpenAPI
    url: openapi/clicksend-post-postcard-api-openapi.yml
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/sms
  - type: APIReference
    url: https://developers.clicksend.com/docs/rest/v3/
  - type: PostmanCollection
    url: collections/clicksend.postman_collection.json
  - type: OpenCollection
    url: collections/clicksend.opencollection.json
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/mms
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/voice-messaging
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/email
  - type: Documentation
    url: https://developers.clicksend.com/docs/post/letters
  - type: Documentation
    url: https://developers.clicksend.com/docs/post/postcards
  - type: Documentation
    url: https://developers.clicksend.com/docs/contacts
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/sms/receive-sms
  - type: Documentation
    url: https://developers.clicksend.com/docs/account
- aid: clicksend:clicksend-receipts-api
  name: ClickSend Receipts API
  description: Delivery receipts, inbound messages, and automations.
  humanURL: https://developers.clicksend.com/docs/messaging/sms
  baseURL: https://rest.clicksend.com/v3
  tags:
  - Receipts
  properties:
  - type: OpenAPI
    url: openapi/clicksend-receipts-api-openapi.yml
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/sms
  - type: APIReference
    url: https://developers.clicksend.com/docs/rest/v3/
  - type: PostmanCollection
    url: collections/clicksend.postman_collection.json
  - type: OpenCollection
    url: collections/clicksend.opencollection.json
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/mms
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/voice-messaging
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/email
  - type: Documentation
    url: https://developers.clicksend.com/docs/post/letters
  - type: Documentation
    url: https://developers.clicksend.com/docs/post/postcards
  - type: Documentation
    url: https://developers.clicksend.com/docs/contacts
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/sms/receive-sms
  - type: Documentation
    url: https://developers.clicksend.com/docs/account
- aid: clicksend:clicksend-sms-api
  name: ClickSend SMS API
  description: Send and view SMS messages.
  humanURL: https://developers.clicksend.com/docs/messaging/sms
  baseURL: https://rest.clicksend.com/v3
  tags:
  - SMS
  properties:
  - type: OpenAPI
    url: openapi/clicksend-sms-api-openapi.yml
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/sms
  - type: APIReference
    url: https://developers.clicksend.com/docs/rest/v3/
  - type: PostmanCollection
    url: collections/clicksend.postman_collection.json
  - type: OpenCollection
    url: collections/clicksend.opencollection.json
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/mms
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/voice-messaging
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/email
  - type: Documentation
    url: https://developers.clicksend.com/docs/post/letters
  - type: Documentation
    url: https://developers.clicksend.com/docs/post/postcards
  - type: Documentation
    url: https://developers.clicksend.com/docs/contacts
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/sms/receive-sms
  - type: Documentation
    url: https://developers.clicksend.com/docs/account
- aid: clicksend:clicksend-voice-api
  name: ClickSend Voice API
  description: Send and view voice (text-to-speech) messages.
  humanURL: https://developers.clicksend.com/docs/messaging/sms
  baseURL: https://rest.clicksend.com/v3
  tags:
  - Voice
  properties:
  - type: OpenAPI
    url: openapi/clicksend-voice-api-openapi.yml
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/sms
  - type: APIReference
    url: https://developers.clicksend.com/docs/rest/v3/
  - type: PostmanCollection
    url: collections/clicksend.postman_collection.json
  - type: OpenCollection
    url: collections/clicksend.opencollection.json
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/mms
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/voice-messaging
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/email
  - type: Documentation
    url: https://developers.clicksend.com/docs/post/letters
  - type: Documentation
    url: https://developers.clicksend.com/docs/post/postcards
  - type: Documentation
    url: https://developers.clicksend.com/docs/contacts
  - type: Documentation
    url: https://developers.clicksend.com/docs/messaging/sms/receive-sms
  - type: Documentation
    url: https://developers.clicksend.com/docs/account
common:
- type: AgenticAccess
  url: agentic-access/clicksend-agentic-access.yml
- type: TrustCenter
  url: security/clicksend-trust-center.yml
- type: DomainSecurity
  url: security/clicksend-domain-security.yml
- type: Authentication
  url: authentication/clicksend-authentication.yml
- type: GitHubOrganization
  url: https://github.com/ClickSend
- type: LinkedIn
  url: https://www.linkedin.com/company/clicksend
- type: Website
  url: https://www.clicksend.com/
- type: Documentation
  url: https://developers.clicksend.com/
- type: Plans
  url: plans/clicksend-plans-pricing.yml
- type: RateLimits
  url: rate-limits/clicksend-rate-limits.yml
- type: FinOps
  url: finops/clicksend-finops.yml
- url: https://blog.clicksend.com/
  type: Blog
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com

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