Postscript

Postscript is an SMS and RCS marketing platform built for Shopify brands, covering list growth, campaign and automation delivery, conversational messaging, AI shopping assistants and TCPA compliance. Its developer surface is the Partner API v2 at api.postscript.io, a twenty-operation REST API authenticated with private API keys, through which partners and enterprise shops read and update SMS subscribers, read opt-in keywords, push custom events into Flow Builder, send promotional, transactional and conversational messages, manage webhook subscriptions for shop and subscriber lifecycle events, and run compliance unsubscribe and redaction operations. A browser JavaScript SDK carries the onsite opt-in popups, the checkout consent checkbox and browse-behaviour event tracking.

Postscript publishes 7 APIs on the APIs.io network, including Subscribers API, Events API, Keywords API, and 4 more. Tagged areas include SMS, Marketing, Messaging, E-Commerce, and Shopify.

The Postscript catalog on APIs.io includes 1 event-driven AsyncAPI specification.

Postscript’s developer surface includes authentication, changelog, documentation, getting-started guide, API reference, pricing, engineering blog, and 36 more developer resources.

🌐 Visit website 📡 Source on GitHub

65.4/100 strong ▬ flat Agent 36/100 agent ready saas Full breakdown ↓
scored 2026-09-08 · rubric v0.20.0

AccessFreemiumSelf serve⚡ Free to try

1 APIs

SMS Marketing Messaging E-Commerce Shopify RCS Subscribers Webhook Compliance

What this lets a business do 2

Business capabilities this provider's published APIs can perform, derived from its own contracts. Browse all capabilities →

Compliance Management

BC-130

Compliance

PATCH /api/v2/compliance/redact PATCH /api/v2/compliance/unsubscribe

Developer Platform & API Ecosystem Management

BC-4270

Webhooks

POST /api/v2/webhooks

Kin Score

Kin Score How this is scored →
scored 2026-09-08 · rubric v0.20.0

Composite quality — 65.4/100 · strong

Contract Quality 12.7 / 19

Developer Ergonomics 6.2 / 15

Access Clarity 14.4 / 15

Operational Transparency 6.2 / 10

Contract Governance 0.4 / 9

Discoverability 5.7 / 8

Regulatory Posture 7.0 / 15

Create-or-Update Ergonomics 2.8 / 10

Agent readiness — 36/100 · agent ready

Machine-Readable Contract 18 / 18

Agentic Access Contract 10 / 10

Documented Reversibility 0 / 6

MCP Server 12 / 12

Machine-Readable Auth 10 / 10

Idempotency 0 / 9

Stable Error Semantics 8 / 8

Request/Response Examples 7 / 7

Rate-Limit Signaling 7 / 7

Typed Event Surface 6 / 6

Agent Skills 5 / 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

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/.

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/postscript: 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 →

APIs 7

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

Postscript Subscribers API

Read, filter, page and update a shop's SMS subscribers. Filters use suffixed operators (__eq, __gt, __contains, __in) across created_at, updated_at, email, phone_number, shopify...

Postscript Events API

Send custom events for use in Postscript Flows and triggers.

Postscript Keywords API

Read the opt-in keywords a shop has configured for subscriber acquisition and attribution.

Postscript Messages API

Send promotional, transactional or conversational SMS and MMS to an existing subscriber, and read the resulting message request and sent message.

Postscript Webhooks API

Create, read, update and delete webhook subscriptions, fetch the Postscript-Signature signing token, retrieve example event payloads and trigger test deliveries.

Postscript Compliance API

TCPA opt-out and data redaction for a subscriber, addressable by subscriber id, phone, email or Shopify customer id.

Postscript Identity API

Verify which partner or shop the calling API token resolves to.

Scroll for all 7

Pricing Plans 1

Published pricing tiers and plan structures.

Postscript Plans Pricing

4 plans

PLANS

Rate Limits 1

Documented rate limits and quota policies.

Postscript Rate Limits

1 limits

RATE LIMITS

FinOps 1

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

Postscript Finops

FINOPS

Event Specifications 1

AsyncAPI definitions for this provider's event-driven and streaming APIs.

Postscript Webhooks

ASYNCAPI

Security Posture 4

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

Postscript Authentication

apiKey · 2 schemes

SECURITY

Postscript Domain Security

TLSv1.3 · HSTS · DMARC

SECURITY

Postscript Vulnerability Disclosure

disclosure policy published

SECURITY

Postscript Trust Center

SOC 2, GDPR

SECURITY

Agentic Access 1

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

Postscript Agentic Access

20 operations · 9 acting

AGENTIC

Resources

Get Started 4

Portal, sign-up, and the first successful call

DeveloperPortal

DeveloperPortal

GettingStarted

GettingStarted

SignUp

SignUp

Login

Documentation 2

Reference material describing how the API behaves

Documentation

Documentation

APIReference

APIReference

Agent Surfaces 5

MCP servers, agent skills, and machine-readable catalogs

AgenticAccess

AgenticAccess

X-MCPServerCandidate

AgentSkill

LLMsTxt

LlmsText

Design & Contract 7

Pagination, idempotency, versioning, errors, and events

Conventions

Conformance

ErrorCatalog

Lifecycle

DataModel

Components

Webhooks

Scroll for all 7

Build 3

SDKs, sample code, and the tooling you integrate with

Packages

Packages

ToolCrosswalk

ToolCrosswalk

SDKs

SDKs

Access & Security 7

Authentication, authorization, and security posture

TrustCenter

TrustCenter

VulnerabilityDisclosure

VulnerabilityDisclosure

Security

DomainSecurity

Authentication

Authentication

Compliance

Scroll for all 7

Operate 6

Status, limits, changes, and where to get help

StatusPage

RateLimits

ChangeLog

RateLimits

ChangeLog

Support

Commercial 5

Pricing, plans, and the legal terms of use

Plans

Plans

Pricing

Pricing

TermsOfService

TermsOfService

APITermsOfService

APITermsOfService

PrivacyPolicy

PrivacyPolicy

Company 3

The organization behind the API

LinkedIn

Website

Website

Blog

Blog

Other 1

Properties that don't map to a standard resource type

CapabilityMap

CapabilityMap

Source (apis.yml)

aid: postscript
name: Postscript
description: Postscript is an SMS and RCS marketing platform built for Shopify brands, covering list growth, campaign and
  automation delivery, conversational messaging, AI shopping assistants and TCPA compliance. Its developer surface is the
  Partner API v2 at api.postscript.io, a twenty-operation REST API authenticated with private API keys, through which partners
  and enterprise shops read and update SMS subscribers, read opt-in keywords, push custom events into Flow Builder, send promotional,
  transactional and conversational messages, manage webhook subscriptions for shop and subscriber lifecycle events, and run
  compliance unsubscribe and redaction operations. A browser JavaScript SDK carries the onsite opt-in popups, the checkout
  consent checkbox and browse-behaviour event tracking.
type: Index
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: freemium
  onboarding: self-serve
  trial: false
  try_now: true
  public: false
  label: Freemium · Self-serve signup
  confidence: high
  source:
  - plans
  - authentication
  - rate-limits
  - security
  - sandbox
  generated: '2026-09-03'
  method: derived
image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/icons/postscript.png
tags:
- SMS
- Marketing
- Messaging
- E-Commerce
- Shopify
- RCS
- Subscribers
- Webhook
- Compliance
tags_raw:
- SMS
- Marketing
- Messaging
- E-commerce
- Shopify
- RCS
- Subscribers
- Webhooks
- Compliance
url: https://raw.githubusercontent.com/api-evangelist/postscript/refs/heads/main/apis.yml
created: '2025-01-01'
modified: '2026-08-13'
specificationVersion: '0.23'
apis:
- aid: postscript:postscript-subscribers-api
  name: Postscript Subscribers API
  description: Read, filter, page and update a shop's SMS subscribers. Filters use suffixed operators (__eq, __gt, __contains,
    __in) across created_at, updated_at, email, phone_number, shopify_customer_id and ps_id.
  humanURL: https://developers.postscript.io/reference/get-subscribers
  baseURL: https://api.postscript.io
  tags:
  - Subscribers
  properties:
  - type: OpenAPI
    url: openapi/postscript-subscribers-api-openapi.yml
  - type: Overlay
    url: overlays/postscript-subscribers-api-overlay.yaml
- aid: postscript:postscript-events-api
  name: Postscript Events API
  description: Send custom events for use in Postscript Flows and triggers.
  humanURL: https://developers.postscript.io/reference/create-custom-event
  baseURL: https://api.postscript.io
  tags:
  - Event
  tags_raw:
  - Events
  properties:
  - type: OpenAPI
    url: openapi/postscript-events-api-openapi.yml
  - type: Overlay
    url: overlays/postscript-events-api-overlay.yaml
- aid: postscript:postscript-keywords-api
  name: Postscript Keywords API
  description: Read the opt-in keywords a shop has configured for subscriber acquisition and attribution.
  humanURL: https://developers.postscript.io/reference/get-keywords
  baseURL: https://api.postscript.io
  tags:
  - Keywords
  properties:
  - type: OpenAPI
    url: openapi/postscript-keywords-api-openapi.yml
  - type: Overlay
    url: overlays/postscript-keywords-api-overlay.yaml
- aid: postscript:postscript-messages-api
  name: Postscript Messages API
  description: Send promotional, transactional or conversational SMS and MMS to an existing subscriber, and read the resulting
    message request and sent message.
  humanURL: https://developers.postscript.io/reference/create-message
  baseURL: https://api.postscript.io
  tags:
  - Message
  - SMS
  tags_raw:
  - Messages
  - SMS
  properties:
  - type: OpenAPI
    url: openapi/postscript-messages-api-openapi.yml
  - type: Overlay
    url: overlays/postscript-messages-api-overlay.yaml
- aid: postscript:postscript-webhooks-api
  name: Postscript Webhooks API
  description: Create, read, update and delete webhook subscriptions, fetch the Postscript-Signature signing token, retrieve
    example event payloads and trigger test deliveries.
  humanURL: https://developers.postscript.io/docs/configuring-webhooks
  baseURL: https://api.postscript.io
  tags:
  - Webhook
  - Event
  tags_raw:
  - Webhooks
  - Events
  properties:
  - type: OpenAPI
    url: openapi/postscript-webhooks-api-openapi.yml
  - type: Overlay
    url: overlays/postscript-webhooks-api-overlay.yaml
  - type: Webhooks
    url: asyncapi/postscript-webhooks.yml
- aid: postscript:postscript-compliance-api
  name: Postscript Compliance API
  description: TCPA opt-out and data redaction for a subscriber, addressable by subscriber id, phone, email or Shopify customer
    id.
  humanURL: https://developers.postscript.io/reference/unsubscribe
  baseURL: https://api.postscript.io
  tags:
  - Compliance
  - Subscribers
  properties:
  - type: OpenAPI
    url: openapi/postscript-compliance-api-openapi.yml
  - type: Overlay
    url: overlays/postscript-compliance-api-overlay.yaml
- aid: postscript:postscript-identity-api
  name: Postscript Identity API
  description: Verify which partner or shop the calling API token resolves to.
  humanURL: https://developers.postscript.io/reference/verify-identity
  baseURL: https://api.postscript.io
  tags:
  - Identity
  properties:
  - type: OpenAPI
    url: openapi/postscript-identity-api-openapi.yml
  - type: Overlay
    url: overlays/postscript-identity-api-overlay.yaml
common:
- type: CapabilityMap
  url: capabilities/postscript-capability-edges.yml
  name: Postscript Business Capability Map
- type: AgenticAccess
  url: agentic-access/postscript-agentic-access.yml
- type: TrustCenter
  url: security/postscript-trust-center.yml
- type: VulnerabilityDisclosure
  url: security/postscript-vulnerability-disclosure.yml
- type: Security
  url: https://postscript.io/security
- type: DomainSecurity
  url: security/postscript-domain-security.yml
- type: Authentication
  url: authentication/postscript-authentication.yml
- type: Conventions
  url: conventions/postscript-conventions.yml
- type: Conformance
  url: conformance/postscript-conformance.yml
- type: ErrorCatalog
  url: errors/postscript-error-codes.yml
- type: Lifecycle
  url: lifecycle/postscript-lifecycle.yml
- type: StatusPage
  url: https://status.postscript.io
- type: DataModel
  url: data-model/postscript-data-model.yml
- type: Packages
  url: packages/postscript-packages.yml
- type: Components
  url: components/postscript-components.yml
- type: X-MCPServerCandidate
  url: mcp/postscript-mcp.yml
  note: 'Renamed from MCPServer 2026-09-03 (roadmap#247): the manifest self-describes as status: candidate — a tool list derived
    from the published API contracts, not an existing server. The scorer already read the manifest and reported mcp_server
    correctly; the MCPServer type was crediting the artifact-type surfaces with a server that does not exist.'
- type: ToolCrosswalk
  url: mcp/postscript-tool-crosswalk.yml
- type: AgentSkill
  url: skills/_index.yml
- type: Webhooks
  url: asyncapi/postscript-webhooks.yml
- type: LLMsTxt
  url: llms/postscript-llms.txt
- type: Plans
  url: plans/postscript-plans-pricing.yml
- type: RateLimits
  url: rate-limits/postscript-rate-limits.yml
- type: ChangeLog
  url: changelog/postscript-changelog.yml
- type: LinkedIn
  url: https://www.linkedin.com/company/postscriptio
- type: Website
  url: https://postscript.io
- type: DeveloperPortal
  url: https://developers.postscript.io
- type: Documentation
  url: https://developers.postscript.io
- type: GettingStarted
  url: https://developers.postscript.io/docs/getting-started
- type: Authentication
  url: https://developers.postscript.io/docs/api-authentication
- type: RateLimits
  url: https://developers.postscript.io/docs/rate-limits
- type: Compliance
  url: https://developers.postscript.io/docs/compliance
- type: APIReference
  url: https://developers.postscript.io/reference
- type: ChangeLog
  url: https://developers.postscript.io/changelog
- type: SDKs
  url: https://developers.postscript.io/docs/javascript-sdk-api-reference
- type: Integrations
  url: https://developers.postscript.io/docs/how-to-use-zapier-with-our-api
- type: Pricing
  url: https://postscript.io/pricing
- type: Blog
  url: https://postscript.io/blog
- type: Support
  url: https://help.postscript.io
- type: SignUp
  url: https://postscript.io/partners-signup
- type: Login
  url: https://app.postscript.io/login
- type: TermsOfService
  url: https://postscript.io/terms-of-service
- type: APITermsOfService
  url: https://postscript.io/api-terms-of-service
- type: PrivacyPolicy
  url: https://postscript.io/privacy
- type: LlmsText
  url: https://developers.postscript.io/llms.txt
integrations:
- name: Postscript
- name: True Classic CaseStudy-FEATURE IMG
- name: Integration-hero_img
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com
x-enrichment:
  date: '2026-08-13'
  status: enriched
  artifacts_added: 33
  pass: local-v1

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