01 · Records and state owned
Subscriber counts, post performance, revenue, retention, traffic data, dashboard metrics, and publication settings.
Substack
Substack
A major newsletter and creator platform included as a useful boundary case: strategically important and widely used, but materially less open to customer-built operational interfaces than API-first peers.
Publishing, newsletters & creator platformsSystem of engagementApplication-bound
Concrete capability record
Data, retrieval, actions, identity, and operating limits
A field-by-field summary of what the reviewed first-party references actually support. Publisher update dates and BYO-UI review dates are shown separately below.
02 · Data you can retrieve
Subscriber counts, post performance, revenue, retention, traffic data, dashboard metrics, and publication settings.
03 · Actions and write paths
Read-only. It cannot publish posts, send Notes, modify the account, or access profile/Notes activity.
04 · Authentication and permissions
The user signs in to Substack, authorizes read access, and selects a publication. Only publication Admins can connect, and the selected publication must have Bestseller status.
05 · Monitoring, approval, and recovery
The connector requests read access and performs no publication changes. Limit connections to approved Admins and assistants because results include subscriber, revenue, retention, and settings data.
06 · Limits and caveats
Only publication Admins on Bestseller publications qualify. The server cannot directly access profile data or Notes activity, publish posts, send Notes, or modify the account.
Agent access
MCP support
Official MCP serverSubstack hosted read-only publication MCPCurrent documented service
Support: Official MCP server
Read scope: Subscriber counts, post performance, revenue, retention, traffic data, dashboard metrics, and publication settings.
Write scope: Read-only. It cannot publish posts, send Notes, modify the account, or access profile/Notes activity.
Authentication: Interactive Substack sign-in is followed by read-access approval and selection of an eligible Bestseller publication inside the compatible AI assistant's connection flow for publication data.
Approval boundary: There is no verified write approval path; require an Admin to approve the connector and publication choice before exposing subscriber, revenue, retention, traffic, or settings data.
Protocol does not erase product boundaries.
Confirm the current tool catalog, plan, region, scopes, rate limits, terms, and write behavior before implementation.
Editorial assessment
Access-maturity dimensions
A comparative architecture lens—not a quality score, market ranking, or buying recommendation. Scale: 1–5.
Data access4
Action access2
Event access1
Identity2
Governance3
Agent access4
UI extensibility3
Portability3
Observability3
Documentation4
Proposed customer-shaped experiences
What customers could create on top.
The output could be an export, report, graph, artifact, application, agent, workflow, or downstream feed. These proposals are derived from documented access—not claims that Substack ships them.
Single-platform patterns
- Public publication and market-research reader
- Publication operator cockpit
- Editorial planning room
- Audience and membership explorer
Multi-platform compositions
- Substack + video or creative platform: publication operator cockpit
- Substack + social or distribution system + analytics or commerce system: cross-system decision workspace
Evidence and dates
First-party references, with publisher and review dates separated
“Publisher updated” is shown only when the page exposes an update date. “BYO-UI reviewed” records when this research checked the reference. A missing publisher date is reported as missing—not replaced with the review date.
4 recorded sources
MCP / agent-role validationRepresentative source
https://support.substack.com/hc/en-us/articles/50834026608916-How-to-connect-Substack-to-your-AI-Assistant ↗Hosted endpoint, supported clients, Admin and Bestseller eligibility, publication selection, analytics scope, and explicit unavailable actions
- Publisher updated
- Jul 5, 2026
- BYO-UI reviewed
- Jul 22, 2026
Substack MCP eligibility, authorization, analytics reads, and write exclusions reviewed 2026-07-22
Developer API supportSource inventory
https://support.substack.com/hc/en-us/articles/45099095296916-Substack-Developer-API ↗Official support entry for the limited developer API.
- Publisher updated
- Not stated by publisher
- BYO-UI reviewed
- Jul 10, 2026
Inventory source: structurally normalized; content was not individually reopened in this pass.
HomepageSource inventory
https://substack.com/ ↗Product and publication platform.
- Publisher updated
- Not stated by publisher
- BYO-UI reviewed
- Jul 10, 2026
Inventory source: structurally normalized; content was not individually reopened in this pass.
Support centerSource inventory
https://support.substack.com/ ↗Official product and policy documentation.
- Publisher updated
- Not stated by publisher
- BYO-UI reviewed
- Jul 10, 2026
Inventory source: structurally normalized; content was not individually reopened in this pass.
Verified fact
Tied to cited first-party evidence reviewed for this profile.
Source inventory
Official links recorded for deeper research but not necessarily reopened endpoint by endpoint.
Editorial assessment
System role, maturity interpretation, and architectural boundary.
Proposed design
Interface patterns and compositions—not vendor product claims.