Plunk

Plunk is an open-source (AGPL-3.0) email platform for developers that unifies transactional email, marketing campaigns, contact segmentation and event-driven workflow automation behind a single REST API. It publishes its own OpenAPI 3.1.0 at docs.useplunk.com/openapi.json, declaring next-api.useplunk.com as the production base URL, and authenticates with a two-class Bearer API key where the prefix decides capability — sk_ for every endpoint and pk_ for the client-safe /v1/track tracking call. The API supports Idempotency-Key on both public write endpoints, cursor pagination, a structured error envelope carrying machine codes plus remediation hints, and a documented webhook event catalogue delivered as workflow steps. Every documentation page is also served as Markdown. The entire stack self-hosts with Docker Compose for full data ownership and no per-email costs.

Plunk publishes 5 APIs on the APIs.io network, including Campaigns API, Contacts API, and 3 more. Tagged areas include Email, Transactional Email, Marketing, Automation, and Open-Source.

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

Plunk’s developer surface includes authentication, documentation, changelog, API reference, getting-started guide, support, pricing, and 28 more developer resources.

🌐 Visit website 📡 Source on GitHub

70.6/100 exemplar ▬ flat Agent 36/100 agent ready Full breakdown ↓
scored 2026-08-25 · rubric v0.14.0

AccessFreemiumOpen⚡ Free to try

5 APIs

Email Transactional Email Marketing Automation Open-Source Software-as-a-Service Email API Webhook Segmentation Workflow-Automation Self-Hosted Developer Tools

Kin Score

Kin Score How this is scored →
scored 2026-08-25 · rubric v0.14.0

Composite quality — 70.6/100 · exemplar

Contract Quality 18.1 / 25

Developer Ergonomics 12.7 / 20

Access Clarity 18.4 / 20

Operational Transparency 9.6 / 13

Contract Governance 3.6 / 12

Discoverability 8.2 / 10

Agent readiness — 36/100 · agent ready

Machine-Readable Contract 18 / 18

Agentic Access Contract 10 / 10

Documented Reversibility 0 / 6

MCP Server 0 / 12

Machine-Readable Auth 10 / 10

Idempotency 9 / 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 Surface 0 / 5

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/plunk: 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 5

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

Rate Limits 1

Documented rate limits and quota policies.

Plunk Rate Limits

3 limits

RATE LIMITS

FinOps 1

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

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 3

MCP servers, agent skills, and machine-readable catalogs

AgenticAccess

AgenticAccess

LLMsTxt

LLMsTxt

AgentSkill

AgentSkill

Design & Contract 7

Pagination, idempotency, versioning, errors, and events

Conventions

Idempotency

ErrorCatalog

Lifecycle

DataModel

Webhooks

Conformance

Scroll for all 7

Build 4

SDKs, sample code, and the tooling you integrate with

GitHubOrganization

Packages

SDKs

SourceCode

Access & Security 3

Authentication, authorization, and security posture

DomainSecurity

DomainSecurity

Authentication

Authentication

Compliance

Compliance

Operate 4

Status, limits, changes, and where to get help

RateLimits

StatusPage

ChangeLog

Support

Commercial 5

Pricing, plans, and the legal terms of use

Plans

FinOps

Pricing

TermsOfService

PrivacyPolicy

Company 2

The organization behind the API

LinkedIn

Website

Website

Other 1

Properties that don't map to a standard resource type

Overlay

Overlay

Source (apis.yml)

aid: plunk
url: https://raw.githubusercontent.com/api-evangelist/plunk/refs/heads/main/apis.yml
name: Plunk
kind: company
description: Plunk is an open-source (AGPL-3.0) email platform for developers that unifies transactional email, marketing
  campaigns, contact segmentation and event-driven workflow automation behind a single REST API. It publishes its own OpenAPI
  3.1.0 at docs.useplunk.com/openapi.json, declaring next-api.useplunk.com as the production base URL, and authenticates with
  a two-class Bearer API key where the prefix decides capability — sk_ for every endpoint and pk_ for the client-safe /v1/track
  tracking call. The API supports Idempotency-Key on both public write endpoints, cursor pagination, a structured error envelope
  carrying machine codes plus remediation hints, and a documented webhook event catalogue delivered as workflow steps. Every
  documentation page is also served as Markdown. The entire stack self-hosts with Docker Compose for full data ownership and
  no per-email costs.
accessModel:
  pricing: freemium
  onboarding: open
  trial: false
  try_now: true
  public: true
  label: Freemium · Open access
  confidence: high
  source:
  - plans
  - authentication
  generated: '2026-07-22'
  method: derived
image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/icons/plunk.png
tags:
- Email
- Transactional Email
- Marketing
- Automation
- Open-Source
- Software-as-a-Service
- Email API
- Webhook
- Segmentation
- Workflow-Automation
- Self-Hosted
- Developer Tools
tags_raw:
- Email
- Transactional Email
- Marketing
- Automation
- Open Source
- SaaS
- Email API
- Webhooks
- Segmentation
- Workflow Automation
- Self-Hosted
- Developer Tools
created: '2026-06-20'
modified: '2026-08-13'
specificationVersion: '0.23'
apis:
- aid: plunk:plunk-api
  name: Plunk API
  description: Plunk's own published OpenAPI 3.1.0, served at https://docs.useplunk.com/openapi.json and declaring https://next-api.useplunk.com
    as the production base URL. Covers the public API (transactional send, event tracking, email verification) plus the contacts,
    templates, campaigns and segments resources. Authenticated with a Bearer API key whose prefix decides its capability —
    sk_ for every endpoint except POST /v1/track, which requires pk_. POST /v1/send and POST /v1/track accept an Idempotency-Key
    header. Lists are cursor paginated. This is the first-party contract; the four hand-authored specs below predate it and
    cover the older api.useplunk.com surface.
  humanURL: https://docs.useplunk.com/api-reference/overview
  baseURL: https://next-api.useplunk.com
  tags:
  - Email
  - Transactional
  - Contacts
  - Campaigns
  - Segments
  - Templates
  properties:
  - type: OpenAPI
    url: openapi/_original/plunk-api-openapi.json
  - type: Overlay
    url: overlays/plunk-api-overlay.yaml
  - type: Documentation
    url: https://docs.useplunk.com/api-reference/overview
  - type: APIReference
    url: https://docs.useplunk.com/api-reference/overview
  - type: Authentication
    url: https://docs.useplunk.com/guides/api-keys
  - type: Idempotency
    url: https://docs.useplunk.com/guides/idempotency
  - type: ErrorCatalog
    url: https://docs.useplunk.com/api-reference/errors
  - type: Webhooks
    url: https://docs.useplunk.com/guides/webhooks
  - type: DataModel
    url: data-model/plunk-data-model.yml
  - type: AgentSkill
    url: skills/_index.yml
  - type: GitHub
    url: https://github.com/useplunk/plunk
- aid: plunk:plunk-campaigns-api
  name: Plunk Campaigns API
  description: Create and send marketing campaigns.
  humanURL: https://docs.useplunk.com/api-reference/transactional/send
  baseURL: https://api.useplunk.com/v1
  tags:
  - Campaigns
  properties:
  - type: OpenAPI
    url: openapi/plunk-campaigns-api-openapi.yml
  - type: Documentation
    url: https://docs.useplunk.com/api-reference/transactional/send
  - type: APIReference
    url: https://docs.useplunk.com/api-reference/overview
  - type: PostmanCollection
    url: collections/plunk.postman_collection.json
  - type: OpenCollection
    url: collections/plunk.opencollection.json
  - type: GitHub
    url: https://github.com/useplunk/plunk
  - type: Documentation
    url: https://docs.useplunk.com/api-reference/transactional/track
  - type: Documentation
    url: https://docs.useplunk.com/api-reference/contacts/create
  - type: Documentation
    url: https://docs.useplunk.com/api-reference/campaigns/create
- aid: plunk:plunk-contacts-api
  name: Plunk Contacts API
  description: Manage contacts and their subscription state.
  humanURL: https://docs.useplunk.com/api-reference/transactional/send
  baseURL: https://api.useplunk.com/v1
  tags:
  - Contacts
  properties:
  - type: OpenAPI
    url: openapi/plunk-contacts-api-openapi.yml
  - type: Documentation
    url: https://docs.useplunk.com/api-reference/transactional/send
  - type: APIReference
    url: https://docs.useplunk.com/api-reference/overview
  - type: PostmanCollection
    url: collections/plunk.postman_collection.json
  - type: OpenCollection
    url: collections/plunk.opencollection.json
  - type: GitHub
    url: https://github.com/useplunk/plunk
  - type: Documentation
    url: https://docs.useplunk.com/api-reference/transactional/track
  - type: Documentation
    url: https://docs.useplunk.com/api-reference/contacts/create
  - type: Documentation
    url: https://docs.useplunk.com/api-reference/campaigns/create
- aid: plunk:plunk-events-api
  name: Plunk Events API
  description: Track contact events that drive automations.
  humanURL: https://docs.useplunk.com/api-reference/transactional/send
  baseURL: https://api.useplunk.com/v1
  tags:
  - Event
  tags_raw:
  - Events
  properties:
  - type: OpenAPI
    url: openapi/plunk-events-api-openapi.yml
  - type: Documentation
    url: https://docs.useplunk.com/api-reference/transactional/send
  - type: APIReference
    url: https://docs.useplunk.com/api-reference/overview
  - type: PostmanCollection
    url: collections/plunk.postman_collection.json
  - type: OpenCollection
    url: collections/plunk.opencollection.json
  - type: GitHub
    url: https://github.com/useplunk/plunk
  - type: Documentation
    url: https://docs.useplunk.com/api-reference/transactional/track
  - type: Documentation
    url: https://docs.useplunk.com/api-reference/contacts/create
  - type: Documentation
    url: https://docs.useplunk.com/api-reference/campaigns/create
- aid: plunk:plunk-transactional-api
  name: Plunk Transactional API
  description: Send transactional email.
  humanURL: https://docs.useplunk.com/api-reference/transactional/send
  baseURL: https://api.useplunk.com/v1
  tags:
  - Transactional
  properties:
  - type: OpenAPI
    url: openapi/plunk-transactional-api-openapi.yml
  - type: Documentation
    url: https://docs.useplunk.com/api-reference/transactional/send
  - type: APIReference
    url: https://docs.useplunk.com/api-reference/overview
  - type: PostmanCollection
    url: collections/plunk.postman_collection.json
  - type: OpenCollection
    url: collections/plunk.opencollection.json
  - type: GitHub
    url: https://github.com/useplunk/plunk
  - type: Documentation
    url: https://docs.useplunk.com/api-reference/transactional/track
  - type: Documentation
    url: https://docs.useplunk.com/api-reference/contacts/create
  - type: Documentation
    url: https://docs.useplunk.com/api-reference/campaigns/create
common:
- type: AgenticAccess
  url: agentic-access/plunk-agentic-access.yml
- type: DomainSecurity
  url: security/plunk-domain-security.yml
- type: Authentication
  url: authentication/plunk-authentication.yml
- type: GitHubOrganization
  url: https://github.com/useplunk
- type: LinkedIn
  url: https://www.linkedin.com/company/useplunk
- type: Website
  url: https://www.useplunk.com
- type: Documentation
  url: https://docs.useplunk.com
- type: Plans
  url: plans/plunk-plans-pricing.yml
- type: RateLimits
  url: rate-limits/plunk-rate-limits.yml
- type: FinOps
  url: finops/plunk-finops.yml
- type: Packages
  url: packages/plunk-packages.yml
- type: SDKs
  url: packages/plunk-packages.yml
- type: LLMsTxt
  url: llms/plunk-llms.txt
- type: Overlay
  url: overlays/plunk-api-overlay.yaml
- type: Conventions
  url: conventions/plunk-conventions.yml
- type: Idempotency
  url: conventions/plunk-conventions.yml
- type: ErrorCatalog
  url: errors/plunk-problem-types.yml
- type: Lifecycle
  url: lifecycle/plunk-lifecycle.yml
- type: StatusPage
  url: https://status.useplunk.com
- type: ChangeLog
  url: changelog/plunk-changelog.yml
- type: DataModel
  url: data-model/plunk-data-model.yml
- type: Webhooks
  url: asyncapi/plunk-webhooks.yml
- type: AgentSkill
  url: skills/_index.yml
- type: Conformance
  url: conformance/plunk-conformance.yml
- type: Compliance
  url: https://www.useplunk.com/dpa
- type: DeveloperPortal
  url: https://docs.useplunk.com
- type: APIReference
  url: https://docs.useplunk.com/api-reference/overview
- type: GettingStarted
  url: https://docs.useplunk.com
- type: Support
  url: https://www.useplunk.com/discord
- type: Pricing
  url: https://www.useplunk.com/pricing
- type: SignUp
  url: https://next-app.useplunk.com/auth/signup
- type: Login
  url: https://next-app.useplunk.com/auth/login
- type: TermsOfService
  url: https://www.useplunk.com/terms
- type: PrivacyPolicy
  url: https://www.useplunk.com/privacy
- type: SourceCode
  url: https://github.com/useplunk/plunk
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com
x-enrichment:
  date: '2026-08-13'
  status: enriched
  artifacts_added: 19
  pass: local-v1

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