Substack MCP Server

preflight_draft

Read-only

Check a Substack draft for title, audience, body structure, images, and paywall issues. Identifies potential problems before publishing, without modifying or publishing the draft.

Instructions

Read a draft and check title, audience, body structure, images and paywalls. Static review aid only: never modifies or publishes; does not guarantee rendering, link availability or publish readiness. Review the findings in Substack.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`draft_id`	Yes

Output Schema

TableJSON Schema

Name	Required	Description	Default
`counts`	Yes
`draft_id`	Yes
`findings`	Yes
`editor_url`	Yes
`limitations`	Yes
`publication`	Yes
`checks_passed`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

AddedSep 8, 2026

TDQS

A4.7/5.0

Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

The description fully discloses that the tool is read-only and non-destructive, aligning with the readOnlyHint annotation and adding concrete details about what it does not guarantee.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is concise, well-structured in three sentences, and covers the essential aspects without unnecessary verbosity.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

It provides sufficient context about what the tool does, its limitations, and where to review results (Substack), making it complete given the output schema exists.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The only parameter, draft_id, is not described in the schema (0% coverage) and the description does not explicitly explain it beyond the tool's context, so it only partially compensates for the missing schema documentation.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool reads a draft and checks specific aspects (title, audience, body structure, images, paywalls), making its purpose unambiguous.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

It explicitly notes it is a static review aid that never modifies or publishes, and it clarifies limitations (no rendering/link/publish guarantees), guiding appropriate usage.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.