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
Substack account sign-in and connector authorization The connecting user must be a publication Admin and the publication must currently qualify as a Bestseller publication.
05 · Monitoring, approval, and recovery
No write approval is needed for the verified surface, but publication financial and subscriber data should be exposed only to approved assistants and users. Eligibility is limited to Bestseller publications. The surface cannot access profile data or Notes activity and cannot make publication or account changes.
06 · Gaps and implementation limits
Eligibility is limited to Bestseller publications. The surface cannot access profile data or Notes activity and cannot make publication or account changes.
Agent access
MCP and adjacent posture
Verified first-party provider MCPSubstack hosted read-only publication MCPCurrent documented service
Role: provider
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: Substack account sign-in and connector authorization
Approval boundary: No write approval is needed for the verified surface, but publication financial and subscriber data should be exposed only to approved assistants and users.
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 interfaces
What customers could build on top.
These are design proposals derived from documented access—not claims that Substack ships these experiences.
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 ↗Substack documents a hosted server for real-time publication analysis in compatible AI assistants.
- Publisher updated
- Not stated by publisher
- BYO-UI reviewed
- Jul 10, 2026
Targeted first-party MCP/agent-role review; broader API inventory retained
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.
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.
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 the representative first-party source or targeted access review.
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.