substack-saved-mcp

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list_saved_posts

Browse and filter cached saved Substack posts by publication, audience, and read state, with pagination and sorting to find what to read next.

Instructions

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

sort_by can be 'saved_at', 'published_at', 'read_progress', or 'minutes_remaining'. 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

TableJSON Schema

Name	Required	Default
`limit`	No
`offset`	No
`sort_by`	No	saved_at
`audience`	No
`read_state`	No
`publication`	No

Output Schema

TableJSON Schema

Name	Required	Description	Default
`result`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

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

A3.6/5.0

Behavior3/5

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

With no annotations, the description carries the full behavioral burden. It discloses non-obvious semantics (the 'unfinished'/'started' groupings, the high-water threshold defaulting to 0.95, and that results are cached), but says nothing about authorization needs, staleness of the cache, or whether the read is safe/non-mutating.

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?

Front-loaded with the core action, then grouped parameter guidance with no filler sentences. The block is somewhat long but every line conveys distinct filter semantics.

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?

An output schema exists, so return values need not be described. For a 6-parameter, 0%-schema-coverage tool the description covers the semantically hard filters well, though the three remaining parameters (limit, offset, publication) are only implied.

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 sort_by values, explains the audience tier concept with a sibling reference, and defines each read_state value precisely. It leaves limit, offset (pagination is only mentioned), and publication unexplained, which keeps it short of a 5.

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?

States a specific verb+resource ('List cached saved posts') plus the scope of its filters. It doesn't explicitly distinguish itself from the nearby search_saved_posts, though 'cached' and the filter set gesture at the difference.

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

Usage Guidelines3/5

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

It routes the agent to list_audiences for valid audience values, which is genuine usage guidance. However, there is no statement of when to use this versus search_saved_posts or saved_posts_status, so the primary selection decision is left to inference.

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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