# Substack

**Canonical:** https://apis.io/providers/substack/  
**Website:** https://substack.com/  
**APIs profiled:** 3

Substack is an independent newsletter and media platform that lets writers, podcasters, video creators, and other culture makers publish directly to readers and monetize through paid subscriptions. Founded in 2017 by Chris Best (CEO), Jairaj Sethi (CTO), and Hamish McKenzie (CWO) and headquartered in San Francisco with a New York City office, Substack provides built-in subscription billing, paid posts, podcasting, chat, video, Notes, and a cross-publication recommendations network. Creators keep 90 percent of subscription revenue (less credit card fees) and own their mailing lists and content. The platform reports more than five million paid subscriptions and tens of millions of weekly active readers. Substack does not offer a general-purpose public REST API for managing publications, posts, or subscribers. It does publish a narrowly scoped official Developer API (released April 2026) that allows token-authenticated lookup of public Substack profiles by LinkedIn handle, gated by an application and Terms-of-Use process. Substack also runs an official remote MCP server at https://mcp.substack.com/api/v1/mcp, documented August 2026, which gives an MCP-capable AI assistant read-only access to publication analytics under OAuth 2.1 with the mcp:read scope, gated to Admins of Bestseller publications. Read access to public content is otherwise available via per-publication RSS feeds, and the broader integration ecosystem relies on reverse-engineered, unofficial JSON endpoints used by the Substack web application. Substack publishes no OpenAPI, no AsyncAPI, no webhooks and no first-party SDK in any package registry.

## Kin Score — 32.2 / 100 (thin)

Scored 2026-08-25 under rubric 0.14.0. Trend: flat (-0.8 from 33.0).

| Facet | Score |
|---|---|
| Discoverability | 74.1 |
| Contract Quality | 0.0 |
| Governance | 18.2 |
| Contract Governance | 18.2 |
| Operational Transparency | 28.9 |
| Developer Ergonomics | 28.6 |
| Commercial Clarity | 65.8 |
| Access Clarity | 65.8 |

## Agent readiness — 11.4 (agent-aware)

| Dimension | Value |
|---|---|
| Spec Presence | no |
| Agentic Access | no |
| Reversibility Documented | no |
| MCP Server | documented |
| Auth Clarity | bearer |
| Idempotency | no |
| Error Semantics | documented |
| OpenAPI Examples | no |
| Rate Limit Signal | documented |
| Event Surface Described | no |
| Agent Skills | no |
| Well Known Catalog | no |
| Consent Identity | no |
| Agent Card | no |
| Dry Run Mode | no |
| Delegated Identity | no |
| Protected Resource Metadata | no |
| Dynamic Client Registration | no |
| Agentic Commerce | no |

## Access

Unknown — onboarding: unknown, pricing: unknown, trial: no (confidence: low).

## APIs (3)

- **Substack Developer API** — Narrowly scoped official API that returns public Substack profile data for a given LinkedIn handle. Access requires accepting the Developer API Terms of Use, applying via form, ...
- **Substack MCP Server** — Official remote Model Context Protocol server that connects a Substack publication to an MCP-capable AI assistant (Claude, ChatGPT, Cursor). Read-only: it serves publication das...
- **Substack RSS Feeds** — Per-publication public RSS feeds available at https://{publication}.substack.com/feed for syndication and read-only access to posts. RSS 2.0 with the content, dc, atom and itune...

## MCP servers (1)

- **Substack**

## Security (3)

- **Substack Authentication** — oauth2/openIdConnect/http · 4 schemes
- **Substack Domain Security** — TLSv1.3 · HSTS · DMARC
- **Substack Vulnerability Disclosure** — disclosure policy published

## Plans (1)

- **Substack Plans Pricing**

## Tags

Newsletters, Publishing, Creator Economy, Subscription, Email, Podcasting, Notes, Media, Independent Media, Paid Content, MCP, Agents, RSS, Analytics

---

Profiled by [API Evangelist](https://apievangelist.com) and published on [APIs.io](https://apis.io/providers/substack/). Scores are computed from the provider's own public artifacts under a published rubric.