substack-saved-mcp

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list_saved_posts

Browse cached saved Substack posts with pagination and filters for publication, audience, and reading state; optionally review reading history to see viewed, saved, or unfinished posts.

Instructions

List cached saved posts with pagination and optional publication/audience filters.

history=True lists the reading history instead: posts viewed on Substack (seen_at set), saved or not (is_saved tells which), newest view first. sort_by can be 'saved_at' (default), 'published_at', 'read_progress', 'minutes_remaining', or 'seen_at' (default with history=True). audience filters by tier (see list_audiences for cached values, e.g. "everyone", "only_paid"). read_state filters by reading progress: 'unread', 'in_progress', 'finished', 'unfinished' (unread + in_progress), or 'started' — a post is 'finished' once its high-water reading progress crosses a threshold, default 0.95.

Input Schema

Name	Required	Description	Default
`limit`	No
`offset`	No
`history`	No
`sort_by`	No
`audience`	No
`read_state`	No
`publication`	No

Output Schema

Name	Required	Description	Default
`result`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

Changed5 schema fields changedv0.4.0Nov 1, 2026

addedInput schema / properties / history

Added value: +{
+  "default": false,
+  "type": "boolean"
+}

addedInput schema / properties / sort_by / anyOf

Added value: +[
+  {
+    "type": "string"
+  },
+  {
+    "type": "null"
+  }
+]

changedInput schema / properties / sort_by / default
```
Previous value: -"saved_at"New value: +null
```
removedInput schema / properties / sort_by / type
```
Removed value: -"string"
```

addedOutput schema / properties / result / items / properties / seen_at

Added value: +{
+  "anyOf": [
+    {
+      "type": "string"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "default": null
+}

Changed7 schema fields changedv0.3.1Aug 22, 2026

addedInput schema / properties / read_state

Added value: +{
+  "anyOf": [
+    {
+      "type": "string"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "default": null
+}

addedOutput schema / properties / result / items / properties / is_fully_read
```
Added value: +{
+  "readOnly": true,
+  "type": "boolean"
+}
```
addedOutput schema / properties / result / items / properties / is_viewed
```
Added value: +{
+  "default": 0,
+  "type": "integer"
+}
```

addedOutput schema / properties / result / items / properties / max_read_progress

Added value: +{
+  "anyOf": [
+    {
+      "type": "number"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "default": null
+}

addedOutput schema / properties / result / items / properties / minutes_remaining

Added value: +{
+  "anyOf": [
+    {
+      "type": "integer"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "readOnly": true
+}

addedOutput schema / properties / result / items / properties / read_progress

Added value: +{
+  "anyOf": [
+    {
+      "type": "number"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "default": null
+}

changedOutput schema / properties / result / items / required

Previous value: -[
-  "url",
-  "title",
-  "publication_name"
-]New value: +[
+  "url",
+  "title",
+  "publication_name",
+  "is_fully_read",
+  "minutes_remaining"
+]

First observedv0.1.0Aug 2, 2026

TDQS

A3.9/5.0

Behavior3/5

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

With no annotations at all, the description carries the full behavioral burden; it does disclose that results come from a cache, that history is ordered 'newest view first', and the (configurable) threshold that defines 'finished'. However it says nothing about cache staleness or that sync_saved_posts / sync_reading_history may be needed when the cache is empty, which is significant for a cache-backed read tool with sync siblings.

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

Conciseness4/5

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

The core purpose is front-loaded in the first sentence, with mode-specific details following in a logical order (history, sort_by, audience, read_state). The parenthetical threshold caveat is slightly long-winded but carries real semantic weight. No filler or repetition.

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?

An output schema exists, so return shape need not be described, and the description covers mode selection, sorting, filtering, and default-value shifts for the 7 optional parameters. The only meaningful omission is cache-freshness/sync guidance, which is a nice-to-have rather than something blocking correct invocation.

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

Parameters4/5

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

Schema description coverage is 0%, so the description must compensate, and it largely does: it enumerates all valid sort_by values and their defaults, defines every read_state value including the composite 'unfinished', and explains audience tiers with examples plus a pointer to list_audiences. Gaps remain for 'publication' (is it a name, id, or slug?) and for limit/offset, which are only covered by the generic word 'pagination'.

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

Purpose4/5

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

The opening sentence names a specific verb and resource ('List cached saved posts') and immediately scopes it with pagination and publication/audience filters. The 'cached' qualifier implicitly separates it from live-fetch siblings like get_post_content, and the history=True paragraph carves out a distinct mode. It never names a sibling it is not, so differentiation is inferable rather than explicit.

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 clearly states the two main usage modes (default saved posts vs. history=True for reading history) and explains that sorting defaults shift per mode. It routes the agent to list_audiences for valid audience values, which is real alternative-routing. It omits when an agent should prefer search_saved_posts or get_saved_post instead of this list tool.

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

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