WriteStack

WriteStack is a Substack growth platform that helps creators schedule, analyze, and monetize their Substack newsletters. It offers tools to draft notes, schedule posts, track audience engagement, and provides a writing coach to generate outlines. The service aims to streamline content creation, improve subscriber growth, and give creators analytics to optimize their newsletters.

WriteStack is listed with 2 APIs on the APIs.io network. Tagged areas include Company, Substack, Growth, Analytics, and ContentCreation.

The WriteStack catalog on APIs.io includes 1 event-driven AsyncAPI specification, 1 JSON-LD context, and 1 Spectral governance ruleset.

WriteStack’s developer surface includes authentication, documentation, getting-started guide, engineering blog, pricing, and 17 more developer resources.

🌐 Visit website 📡 Profile data on GitHub

40.3/100 developing Agent 39/100 agent ready Full breakdown ↓
scored 2026-10-31 · rubric v0.25.0 · Show this score on your site →

2 APIs

CompanySubstackGrowth AnalyticsContentCreation

Kin Score

Kin Score How this is scored →
scored 2026-10-31 · rubric v0.25.0

Composite quality — 40.3/100 · developing

Contract Quality 6.0 / 21

Developer Ergonomics 7.7 / 17

Access Clarity 10.7 / 17

Operational Transparency 2.0 / 11

Contract Governance 2.0 / 10

Discoverability 4.6 / 9

Regulatory Posture 3.7 / 15

Agent readiness — 39/100 · agent ready

Machine-Readable Contract 18 / 18

Agentic Access Contract 0 / 10

Documented Reversibility 0 / 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 0 / 7

Typed Event Surface 6 / 6

Agent Skills 0 / 5

Well-Known Catalog 4 / 4

Consent & Bot Identity 0 / 3

A2A Agent Card 0 / 8

Dry-Run / Simulate Mode 0 / 4

Delegated User Identity 6 / 6

Protected Resource Metadata 5 / 5

Registration Without a Human 6 / 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 Horizontal (data, software, accessibility, platform) 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 could not be measured. We hold no machine-readable contract for this provider to read, so there is nothing to measure a write surface against. Excluded rather than scored zero: never-measured and measured-empty are different facts. Publishing an OpenAPI is what makes this facet — and several others — scorable at all.

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/.

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Agent readiness — checks not met, largest first (exact, from this profile):

MCP Server +12 pts — deployment.mode + probe verdict on the mcp/ manifest, not the pointer; an unprobed slug falls back to authorship
Agentic Access Contract +10 pts — agentic_access artifact present (x-agentic-access), graded by author
Idempotency +9 pts — OpenAPI mutating operations declare an idempotency key — a header, a request-body property, or a named de-duplication token whose own description says so (verified); else common[].type matches /idempoten/i (documented)
A2A Agent Card +8 pts — a2a/-a2a.yml manifest, graded on conformance.grade against A2A 1.0.0
Stable Error Semantics +8 pts — OpenAPI $refs a shared error schema across 4xx/5xx responses (verified), else common[].type includes ErrorCatalog / ErrorCodes / DeclineCodes
Rate-Limit Signaling +7 pts — OpenAPI responses document X-RateLimit-* / RateLimit headers (verified), else a rate_limits artifact or RateLimits link (documented)

6 more unmet checks in the Agent Readiness table above.

Kin Score — facets with the most composite points still available (weight × headroom):

Contract Quality scores 28.2 — up to +18.0 composite points
Developer Ergonomics scores 45.2 — up to +11.0 composite points
Operational Transparency scores 18.4 — up to +10.6 composite points

Each check links to what satisfies it. Publish the artifact, or tell us where it already lives, and the score moves on the next scoring run.

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 the provider profile at artifacts.apis.io/writestack/apis.yml: open an issue on github.com/api-evangelist/writestack to ask a question or point us at an artifact you publish. Submit an artifact on GitHub — free → Manage your own listing — the Influence plan, $499/mo →

APIs 2

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

WriteStack API

WriteStack provides tools for Substack creators to schedule, analyze, and monetize newsletters via a developer portal.

WriteStack API

WriteStack API as documented publicly: 20 operations. Contract generated from the documentation by API Evangelist (2026-10-27); not the provider's own document.

Pricing Plans 1

Published pricing tiers and plan structures.

Writestack Plans Pricing

3 plans

PLANS

Event Specifications 1

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

Writestack Webhooks

ASYNCAPI

Semantic Vocabularies 1

JSON-LD contexts and semantic vocabularies used across these APIs.

Writestack Context

4 classes · 6 properties

JSON-LD

Spectral Rules 1

Spectral governance rulesets for linting and validating these APIs.

WriteStack API Rules

11 rules · 10 errors 1 info

SPECTRAL

JSON Schema 4

Standalone JSON Schema definitions for this provider's data models.

PostV1BillingBuyRequest

2 properties

JSON SCHEMA

PostV1BillingBuyResponse

3 properties

JSON SCHEMA

PostV1RegistrarDomainsPriceRequest

1 properties

JSON SCHEMA

PostV1RegistrarDomainsSearchRequest

1 properties

JSON SCHEMA

Security Posture 2

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

Writestack Authentication

1 scheme

SECURITY

Writestack Domain Security

TLSv1.3 · HSTS · DMARC

SECURITY

Resources

Get Started 2

Portal, sign-up, and the first successful call

DeveloperPortal

DeveloperPortal

GettingStarted

GettingStarted

Documentation 1

Reference material describing how the API behaves

Documentation

Documentation

Agent Surfaces 2

MCP servers, agent skills, and machine-readable catalogs

LLMsTxt

LLMsTxt

WellKnown

WellKnown

Design & Contract 6

Pagination, idempotency, versioning, errors, and events

Spectral

JSONLD

Vocabulary

Webhooks

DataModel

Conformance

Access & Security 3

Authentication, authorization, and security posture

Authentication

Authentication

SecurityTxt

SecurityTxt

DomainSecurity

DomainSecurity

Commercial 4

Pricing, plans, and the legal terms of use

Plans

Pricing

TermsOfService

PrivacyPolicy

Company 2

The organization behind the API

Website

Website

Blog

Blog

Other 2

Properties that don't map to a standard resource type

Hosts

Hosts

Vendors

Vendors

Source (apis.yml)

aid: writestack
name: WriteStack
description: WriteStack is a Substack growth platform that helps creators schedule, analyze, and monetize their Substack newsletters.
  It offers tools to draft notes, schedule posts, track audience engagement, and provides a writing coach to generate outlines.
  The service aims to streamline content creation, improve subscriber growth, and give creators analytics to optimize their
  newsletters.
url: https://raw.githubusercontent.com/api-evangelist/writestack/refs/heads/main/apis.yml
x-type: company
x-source: harvest:new-submission
x-tier: profiled
x-tier-reason: enrichment pass 2026-10-27 (modular-v1; was harvest)
specificationVersion: '0.20'
created: '2026-10-27'
modified: '2026-10-27'
tags:
- Company
- Substack
- Growth
- Analytics
- ContentCreation
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com
- FN: APIs.json
  email: info@apis.io
common:
- type: Plans
  url: plans/writestack-plans-pricing.yml
- type: Spectral
  url: rules/writestack-rules.yml
- type: JSONLD
  url: json-ld/writestack-context.jsonld
- type: Vocabulary
  url: vocabulary/writestack-vocabulary.yml
- type: Webhooks
  url: asyncapi/writestack-webhooks.yml
- type: DataModel
  url: data-model/writestack-data-model.yml
- type: Authentication
  url: authentication/writestack-authentication.yml
- type: Conformance
  url: conformance/writestack-conformance.yml
- type: LLMsTxt
  url: llms/writestack-llms.txt
- type: SecurityTxt
  url: well-known/writestack-vercel-security.txt
- type: WellKnown
  url: well-known/writestack-well-known.yml
- type: Hosts
  url: hosts/writestack-hosts.yml
- type: Vendors
  url: vendors/writestack-vendors.yml
- type: DomainSecurity
  url: security/writestack-domain-security.yml
- type: Website
  url: https://www.writestack.io/
- type: DeveloperPortal
  url: https://www.writestack.io/
- type: Documentation
  url: https://www.writestack.io/tools
- type: GettingStarted
  url: https://www.writestack.io/#pricing
- type: Blog
  url: https://www.writestack.io/blog
- type: Pricing
  url: https://www.writestack.io/pricing.md
- type: TermsOfService
  url: https://www.writestack.io/tos
- type: PrivacyPolicy
  url: https://www.writestack.io/privacy
apis:
- name: WriteStack API
  description: WriteStack provides tools for Substack creators to schedule, analyze, and monetize newsletters via a developer
    portal.
  humanURL: https://www.writestack.io/tools
  baseURL: null
  aid: writestack:writestack-api-2
- aid: writestack:writestack-api
  name: WriteStack API
  description: 'WriteStack API as documented publicly: 20 operations. Contract generated from the documentation by API Evangelist
    (2026-10-27);

    not the provider''s own document.'
  humanURL: https://vercel.com/openapi.json
  properties:
  - type: OpenAPI
    url: openapi/_ae-authored/writestack-openapi-generated.yml
    x-provenance: generated
  - type: JSONSchema
    url: json-schema/writestack-post-v1-billing-buy-response-schema.json
  - type: JSONSchema
    url: json-schema/writestack-post-v1-billing-buy-request-schema.json
  - type: JSONSchema
    url: json-schema/writestack-post-v1-registrar-domains-price-request-schema.json
  - type: JSONSchema
    url: json-schema/writestack-post-v1-registrar-domains-search-request-schema.json
x-submission-probe: 308 (-> https://www.writestack.io/) 2026-10-25
x-coverage:
  state: unreadable
  reason: js-rendered-docs
  detail: The developer portal pages are rendered via JavaScript and no machine‑readable OpenAPI spec was found.
  evidence:
  - url: https://www.writestack.io/tools
    status: 200
  checked: '2026-10-27'
x-enrichment:
  date: '2026-10-27'
  status: enriched
  artifacts_added: 31
  pass: modular-v1
  engine: identity=local,contract=local,surfaces=local,docs=local,regulatory=local

WriteStack API — frequently asked questions

Does WriteStack have an API?

Yes. APIs.io lists 2 APIs from WriteStack, including WriteStack API and WriteStack API.

Is there an OpenAPI specification for the WriteStack API?

Yes. APIs.io indexes 1 OpenAPI specification for WriteStack, each linked for download from this page.

How do I authenticate with the WriteStack API?

WriteStack documents its authentication (1 scheme). The details are profiled on APIs.io as Writestack Authentication.

How much does the WriteStack API cost?

APIs.io lists 3 pricing plans for WriteStack, with each plan's price, limits and inclusions under Pricing Plans on this page.

Is the WriteStack API ready for AI agents?

WriteStack has a Kin Score of 40.3 out of 100 (developing) and an Agent Readiness score of 39.1 (agent-ready), scored by API Evangelist on 2026-10-31.

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