Substack MCP Server

list_published_posts

Read-only

Retrieve published Substack posts with pagination, returning title, date, slug, and URL for each post. Use limit and offset to control the result set.

Instructions

List published posts with pagination. Returns title, date, slug, and URL for each post.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`limit`	No	Max posts to return (1-50; Substack rejects anything higher, so larger values are clamped)
`offset`	No	Number of posts to skip

Output Schema

TableJSON Schema

Name	Required	Description	Default
`posts`	Yes
`total`	No

Schema Changelog

Changes observed during successful MCP inspections.

Changed7 schema fields changedSep 8, 2026

addedInput schema / properties / limit / exclusiveMinimum
```
Added value: +0
```
addedInput schema / properties / limit / maximum
```
Added value: +9007199254740991
```

changedInput schema / properties / limit / type

Previous value: -"number"New value: +"integer"

addedInput schema / properties / offset / maximum
```
Added value: +9007199254740941
```
addedInput schema / properties / offset / minimum
```
Added value: +0
```

changedInput schema / properties / offset / type

Previous value: -"number"New value: +"integer"

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "additionalProperties": false,
+  "properties": {
+    "posts": {
+      "items": {
+        "additionalProperties": false,
+        "properties": {
+          "audience": {
+            "$ref": "#/properties/posts/items/properties/title"
+          },
+          "id": {
+            "exclusiveMinimum": 0,
+            "maximum": 9007199254740991,
+            "type": "integer"
+          },
+          "post_date": {
+            "$ref": "#/properties/posts/items/properties/title"
+          },
+          "slug": {
+            "$ref": "#/properties/posts/items/properties/title"
+          },
+          "subtitle": {
+            "$ref": "#/properties/posts/items/properties/title"
+          },
+          "title": {
+            "type": [
+              "string",
+              "null"
+            ]
+          },
+          "url": {
+            "$ref": "#/properties/posts/items/properties/title"
+          },
+          "word_count": {
+            "$ref": "#/properties/total"
+          }
+        },
+        "required": [
+          "id"
+        ],
+        "type": "object"
+      },
+      "maxItems": 50,
+      "type": "array"
+    },
+    "total": {
+      "anyOf": [
+        {
+          "maximum": 9007199254740991,
+          "minimum": 0,
+          "type": "integer"
+        },
+        {
+          "type": "null"
+        }
+      ]
+    }
+  },
+  "required": [
+    "posts"
+  ],
+  "type": "object"
+}

Changed1 schema field changedv0.6.2Aug 4, 2026

changedInput schema / properties / limit / description

Previous value: -"Max posts to return (1-100)"New value: +"Max posts to return (1-50; Substack rejects anything higher, so larger values are clamped)"

First observedv1.0.0Mar 13, 2026

TDQS

A4.4/5.0

Behavior3/5

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

The readOnlyHint annotation already covers safety; the description adds output details but does not go beyond that, so limited additional transparency.

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?

Two concise sentences, no fluff, and the key purpose is front-loaded.

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?

With an output schema present and a clear mention of return fields, the description is complete for the intended use.

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

Parameters5/5

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

Both parameters (limit and offset) have clear, detailed descriptions including clamping behavior, with full schema coverage.

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?

Clearly states the action ('List published posts') and resource, distinguishing it from similar tools like list_scheduled_posts.

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

Usage Guidelines4/5

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

Provides clear context on pagination and return fields, but does not explicitly mention alternatives or when to prefer this over search_posts.

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