Substack MCP Server

get_post

Read-only

Retrieve full content of a published Substack post by ID, including title, body HTML, and metadata. Use it to fetch post details for reading or processing.

Instructions

Get the full content of a published post by ID. Returns title, body HTML, metadata.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`post_id`	Yes	The post ID to retrieve

Output Schema

TableJSON Schema

Name	Required	Description	Default
`id`	Yes
`url`	No
`slug`	No
`title`	No
`audience`	No
`subtitle`	No
`body_html`	No
`post_date`	No
`word_count`	No

Schema Changelog

Changes observed during successful MCP inspections.

Changed4 schema fields changedSep 8, 2026

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

changedInput schema / properties / post_id / type

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

changedOutput schema / (root)

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

First observedv1.0.0Mar 13, 2026

TDQS

A4/5.0

Behavior3/5

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

The annotation indicates readOnlyHint, which covers the read-only nature. The description adds a constraint that the post must be published, but does not disclose other behavioral aspects such as error handling or side effects. Given the presence of the annotation, this is adequate but not exceptional.

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, consisting of a single sentence that states the action and the expected return data. It is well-structured and front-loaded, making it easy to parse.

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

Completeness4/5

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

For a simple retrieval operation, the description is sufficiently complete: it names the input and output content. It does not address error cases or edge conditions, but given the simplicity and the presence of an output schema, this is not a significant gap.

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 input schema fully describes the only parameter (post_id) with a clear description. The tool description does not add any additional meaning to this parameter, so a baseline score of 3 is appropriate.

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's function: retrieving the full content of a published post by ID, and explicitly mentions the returned data (title, body HTML, metadata). It distinguishes itself from sibling tools by specifying 'published post', 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 Guidelines4/5

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

The description implicitly provides usage guidance by specifying that it operates on published posts, which contrasts with draft-related tools. However, it does not explicitly mention alternatives or when to prefer this tool over others, so it falls short of a 5.

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