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 API contracts indexed on the APIs.io network, including Account API, Contact API, Email 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 📡 Profile data on GitHub

26.9/100 thin ▬ flat Agent 21/100 agent aware Front door AI 2/6 trace saas Full breakdown ↓
scored 2026-10-23 · rubric v0.25.0 · Show this score on your site →

AccessPaid

1 published contract

Communications SMS MMS Voice Email Messaging CPaaS Fax Direct Mail

Kin Score

Kin Score How this is scored →
scored 2026-10-23 · rubric v0.25.0

Composite quality — 26.9/100 · thin

Contract Quality 8.3 / 19

Developer Ergonomics 4.8 / 15

Access Clarity 2.4 / 15

Operational Transparency 1.0 / 10

Contract Governance 0.0 / 9

Discoverability 5.0 / 8

Regulatory Posture 2.1 / 15

Create-or-Update Ergonomics 0.0 / 10

Agent readiness — 21/100 · 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

Delegated User Identity 0 / 6

Protected Resource Metadata 0 / 5

Registration Without a Human 0 / 6

Agentic Commerce Well-Known Document 0 / 5

Pagination 5 / 5

Distinct Operations 3 / 3

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.

Create-or-Update Ergonomics applies to this provider. This API accepts writes, so it carries 10 points of the composite. It is scored from the published contracts themselves: whether a caller can create-or-update in one call, whether the write accepts a key the caller already holds, and whether the response says which branch ran. Without that, every write needs a search-and-branch in front of it, and the first time that check is skipped a duplicate record is created. Scored against the observed mean rather than raw — a provider at the catalog average is unchanged by this facet, not penalised by it.

The six quality facets above are damped to 75 points between them, because the conditional facet above carries the other 25. That is why each facet's contribution is shown against a damped maximum: raising a quality facet moves the composite by 75% of its nominal weight, not 100%. The full arithmetic is at apis.io/rating/.

Show this score on your site.

It updates itself when the score changes. Paste this where you link to your API docs:

<a href="https://apis.io/providers/clicksend/"><img src="https://apis.io/badge/clicksend/card.svg" alt="ClickSend on APIs.io — Kin Score by API Evangelist"></a>

Other styles, a README pill and a shields.io endpoint are on the badge page.

Improve this rating by publishing the missing artifacts — every area above can be raised, and the full rubric is at apis.io/rating/. Every facet and dimension name above is a link: it opens that measurement's own page — what it means, the exact checks that feed it, how the whole catalog distributes on it, and the providers at the top of it. 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. Submit an artifact on GitHub — free → Manage your own listing — the Influence plan, $499/mo →

Markets this provider is in provisional

The Kin Score Market layer reads a provider inside its market: its position, and how deep its integrations go. Depth is only comparable within a position. Provisional and unweighted: not part of the Kin Score or agent readiness.

Market	Position	Depth	Registered MCP server	Declares compatibility
APIs.guru OpenAPI Directory (API definition directory)	undeclared	-	1	-
Airtable Marketplace (extension builders)	undeclared	-	1	-
IFTTT Services (service publishers)	undeclared	-	1	-

Registered MCP server and declares compatibility are report only — not weighted. Undeclared means we found nothing we can read, so there is no number: we never infer integrations.

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 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.

ClickSend Contact List API

Manage contact lists.

Scroll for all 10

Open Collections 11

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

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 11

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 · 21 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

Website

Website

Blog

Blog

Source (apis.yml)

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.
deliveryModel:
  model: saas
  open_source: false
  commercial: true
  callable_host: true
  label: Hosted service · you call their endpoint
  confidence: high
  source:
  - openapi
  - pricing
  generated: '2026-08-28'
  method: derived
accessModel:
  pricing: paid
  onboarding: unknown
  trial: false
  try_now: false
  public: false
  label: Paid
  confidence: medium
  source:
  - plans
  - authentication
  - security
  generated: '2026-09-03'
  method: derived
image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/icons/clicksend.png
tags:
- Communications
- SMS
- MMS
- Voice
- Email
- Messaging
- CPaaS
- Fax
- Direct Mail
tags_raw:
- Communications
- SMS
- MMS
- Voice
- Email
- Post
- Messaging
- CPaaS
- Fax
- Direct Mail
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-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
- aid: clicksend:clicksend-contact-list-api
  name: ClickSend Contact List API
  description: Manage contact lists.
  humanURL: https://developers.clicksend.com/docs/messaging/sms
  baseURL: https://rest.clicksend.com/v3
  tags:
  - Contact List
  properties:
  - type: OpenAPI
    url: openapi/clicksend-contact-list-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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