# MCP Server for AI Agents: Substack Newsletter & Posts API (`mutualistic_housing/substack-newsletter-mcp`) Actor

Standby MCP Server (/mcp) and batch Actor for AI agents to search Substack publications, list newsletter archives, search inside a newsletter and extract full posts as Markdown with podcast audio URLs. No proxy, no login.

- **URL**: https://apify.com/mutualistic_housing/substack-newsletter-mcp.md
- **Developed by:** [Mutualistic Labs](https://apify.com/mutualistic_housing) (community)
- **Categories:** AI, MCP servers
- **Stats:** 1 total users, 0 monthly users, 0.0% runs succeeded, 0 bookmarks
- **User rating**: No ratings yet

## Pricing

Pay per usage

This Actor is paid per platform usage. The Actor is free to use, and you only pay for the Apify platform usage, which gets cheaper the higher subscription plan you have.

Learn more: https://docs.apify.com/actors/running/actors-in-store.md#pay-per-usage

## What's an Apify Actor?

An Actor is a serverless cloud program that runs on the Apify platform. It has two run modes.
In Batch mode, an Actor accepts a well-defined JSON input, performs an action which can take anything from a few seconds to a few hours,
and optionally produces a well-defined JSON output, datasets with results, or files in key-value store.
In Standby mode, an Actor provides a web server which can be used as a website, API, or an MCP server.

Apify vocabulary and the platform model are defined once, in the agent quickstart at https://apify.com/agents.md.

## How to integrate an Actor?

If asked about integration, you help developers integrate Actors into their projects.
You adapt to their stack and deliver integrations that are safe, well-documented, and production-ready.

Do not guess an integration path. Every one of them is in the agent quickstart at https://apify.com/agents.md: the Apify MCP server, Agent Skills with the Apify CLI, the JavaScript and Python clients, the REST API, and the account-free path for an agent with no human to sign in. It also carries the rule on stating cost before the first paid run.

For examples already wired to this Actor's own input schema, see the [API](#api) section below.

Each client library has reference documentation the quickstart does not restate: [JavaScript/TypeScript](https://docs.apify.com/api/client/js/docs.md) (`npm install apify-client`) and [Python](https://docs.apify.com/api/client/python/docs.md) (`pip install apify-client`).

# README

## MCP Server for AI Agents: Substack Newsletter & Posts API

An always-on **Model Context Protocol (MCP) server** and batch Actor that searches **Substack publications**, lists newsletter
archives (newest or top posts, with keyword search **inside** a newsletter) and extracts **full posts and podcast episodes as clean
Markdown** (headings, lists, links and fenced code blocks preserved) including podcast audio URLs. Built for AI agents (Claude
Desktop, Cursor, Windsurf, OpenAI Agents, LangChain), market and competitor research, newsletter monitoring and content analysis.

No proxies, no browser, no logins, no cookies: only the public Substack JSON endpoints (`/api/v1/publication/search`,
`/api/v1/archive`, `/api/v1/posts/{slug}`) are called. Paywalled posts return their public preview and `is_paywalled: true`.

### What you get

| `record_type` | Mode | What it is |
|---|---|---|
| `publication` | `search_publications` | One Substack publication (name, author, tagline, subscriber magnitude, podcast flags) |
| `post` | `archive`, `posts` | One post or podcast episode (metadata, counts, tags, audience, Markdown `content_text`, audio URLs) |

### Endpoints

- `GET /` and `GET /health`: readiness probe, returns `{"status":"ok","actor":"substack-newsletter-mcp",...}`.
- `POST /mcp`: MCP JSON-RPC 2.0 (`initialize`, `ping`, `tools/list`, `tools/call`).

Standby URL: `https://mutualistic-housing--substack-newsletter-mcp.apify.actor/mcp` (authenticate with your Apify API token).

### Input

| Field | Type | Default |
|---|---|---|
| `mode` | `archive`, `search_publications`, `posts` | `archive` |
| `publications` | string\[] (preset keys, subdomains, `*.substack.com` URLs or custom https domains, 1 to 10) | `["pragmaticengineer"]` |
| `query` | string, max 200 chars (required for `search_publications`; optional keyword search inside each newsletter in `archive`) | none |
| `sort` | `new`, `top` | `new` |
| `include_full_text` | boolean | `true` |
| `audience_filter` | `all`, `everyone` (free only), `only_paid` | `all` |
| `post_urls` | string\[] of post URLs (mode `posts`, max 50 together with `slugs`) | none |
| `slugs` | string\[] of post slugs bound to the one explicit publication (mode `posts`) | none |
| `max_items` | integer 1 to 500 | `25` |
| `max_total_charge_usd` | number or null | no cap |

An empty `{}` input runs: the 25 newest posts of `pragmaticengineer` with full text. camelCase aliases (`includeFullText`,
`audienceFilter`, `postUrls`, `maxItems`, `maxTotalChargeUsd`) are accepted. Invalid input is rejected with
`INVALID_INPUT_ZERO_CHARGE` before any network call or charge.

#### Batch input examples

Newest posts of two newsletters, full text:

```json
{"mode": "archive", "publications": ["pragmaticengineer", "lenny"], "max_items": 25}
```

Search inside a newsletter (titles and bodies), top posts, free only:

```json
{"mode": "archive", "publications": ["semianalysis"], "query": "HBM", "sort": "top", "audience_filter": "everyone", "max_items": 20}
```

Find publications:

```json
{"mode": "search_publications", "query": "machine learning", "max_items": 30}
```

Specific posts (URLs, or slugs bound to one publication):

```json
{"mode": "posts", "post_urls": ["https://newsletter.pragmaticengineer.com/p/some-post"]}
```

```json
{"mode": "posts", "publications": ["lenny"], "slugs": ["some-post-slug"]}
```

### MCP tools

```json
{
  "mcpServers": {
    "substack": {
      "url": "https://mutualistic-housing--substack-newsletter-mcp.apify.actor/mcp",
      "headers": { "Authorization": "Bearer <APIFY_TOKEN>" }
    }
  }
}
```

- **`get_newsletter_posts`**: `publications`, `sort`, `search`, `include_full_text` (default `false` in MCP), `audience_filter`, `max_items` (default 10).
- **`search_publications`**: `query` (required), `max_items`.
- **`get_post_content`**: `post_url`, or `publication` + `slug`.
- **`list_preset_publications`**: no arguments; lists the preset publications (free).

Example calls:

```bash
curl -X POST "https://mutualistic-housing--substack-newsletter-mcp.apify.actor/mcp" \
  -H "Authorization: Bearer <APIFY_TOKEN>" \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"get_newsletter_posts","arguments":{"publications":["pragmaticengineer"],"sort":"top","search":"scaling","max_items":5}}}'
```

```json
{"jsonrpc":"2.0","id":2,"method":"tools/call","params":{"name":"search_publications","arguments":{"query":"semiconductors","max_items":10}}}
```

```json
{"jsonrpc":"2.0","id":3,"method":"tools/call","params":{"name":"get_post_content","arguments":{"post_url":"https://newsletter.pragmaticengineer.com/p/some-post"}}}
```

```json
{"jsonrpc":"2.0","id":4,"method":"tools/call","params":{"name":"list_preset_publications","arguments":{}}}
```

### Output fields

`post`:

| Field | Meaning |
|---|---|
| `record_type`, `uid` | `post`; deterministic SHA-256 identifier |
| `post_id`, `publication_id`, `publication_subdomain`, `publication_base_url` | Ids and publication the post belongs to |
| `title`, `subtitle`, `description`, `slug`, `canonical_url`, `post_date` | Post metadata |
| `audience`, `post_type`, `is_paywalled` | `everyone` / `only_paid` / ...; `newsletter` / `podcast` / `thread`; paywall flag |
| `wordcount`, `reaction_count`, `comment_count`, `restacks` | Counts |
| `authors`, `tags`, `section_name`, `cover_image` | Authors, tags, section, cover image |
| `excerpt`, `content_text`, `content_source` | Clean excerpt; full Markdown (up to 100000 characters); `body_html` or `post_endpoint` |

Podcast fields: `podcast_url` (audio URL), `podcast_duration` (seconds) and `audio_items`, a list of
`{"audio_url", "type", "status", "duration"}` entries for every audio attachment of the episode.

`publication`:

| Field | Meaning |
|---|---|
| `record_type`, `uid`, `publication_id` | `publication`; deterministic SHA-256 identifier; Substack id |
| `name`, `subdomain`, `custom_domain`, `base_url` | Name and addresses |
| `author_name`, `author_handle`, `author_bio`, `author_bestseller_tier` | Main author |
| `hero_text`, `language`, `logo_url` | Tagline, language, logo |
| `free_subscriber_magnitude`, `ranking_detail` | Subscriber order of magnitude (e.g. `100K+`) and ranking text |
| `has_podcast`, `has_free_podcast`, `community_enabled` | Feature flags |
| `created_at`, `first_post_date` | Dates |

Example `post` (podcast episode, shortened):

```json
{
  "record_type": "post", "post_id": 1234567, "publication_id": 458709, "publication_subdomain": "pragmaticengineer",
  "publication_base_url": "https://pragmaticengineer.substack.com", "title": "Example episode", "slug": "example-episode",
  "canonical_url": "https://newsletter.pragmaticengineer.com/p/example-episode", "post_date": "2026-01-10T09:00:00.000Z",
  "audience": "everyone", "post_type": "podcast", "wordcount": 4200, "reaction_count": 310, "comment_count": 42, "restacks": 12,
  "authors": ["Gergely Orosz"], "tags": ["AI"], "podcast_url": "https://example.com/audio.mp3", "podcast_duration": 3605.5,
  "audio_items": [{"audio_url": "https://example.com/audio.mp3", "type": "podcast", "status": "transcoded", "duration": 3605.5}],
  "content_text": "# Example episode\n\nIntro...", "content_source": "post_endpoint", "is_paywalled": false, "uid": "<sha256>"
}
```

### Preset publications

Use the key in `publications`; any other Substack subdomain, `*.substack.com` URL or custom newsletter domain works too (https only).

| Key | Publication | Topic |
|---|---|---|
| `pragmaticengineer` | The Pragmatic Engineer | software engineering |
| `lenny` | Lenny's Newsletter | product |
| `semianalysis` | SemiAnalysis | semiconductors, AI |
| `astralcodexten` | Astral Codex Ten | essays, science, rationality |
| `noahpinion` | Noahpinion | economics |
| `slowboring` | Slow Boring | policy |
| `oneusefulthing` | One Useful Thing | AI |
| `garymarcus` | Marcus on AI | AI |
| `thezvi` | Don't Worry About the Vase | AI |
| `simonw` | Simon Willison's Newsletter | AI, development |
| `importai` | Import AI | AI policy |
| `bytebytego` | ByteByteGo Newsletter | system design |
| `latentspace` | Latent Space | AI engineering |
| `thegeneralist` | The Generalist | tech, business |
| `heathercoxrichardson` | Letters from an American | US politics |

### Security and limits

- **https only**: bare names become `https://name.substack.com`; `http://`, `file:` and other schemes are rejected.
- **SSRF protections**: credentials in URLs, non-443 ports, `..` path traversal and fragments are rejected; IP literals, `localhost`,
  `.local` and `.internal` names are blocked; DNS results (and the connected peer address) that are loopback, private, link-local,
  CGNAT, multicast or unspecified are refused. Redirects (for example to a custom domain) must be https and are re-checked per host.
- **Bounds**: at most 500 items per run, 10 publications per call, 50 posts in mode `posts`, a 120 s global batch deadline, a 45 s
  deadline per MCP tool call, a 15 s per-request timeout (connect, TLS, headers and body) and a 2 MiB response size cap.
- **MCP server**: request bodies above 64 KiB return `413`, `POST /mcp` requires `Content-Type: application/json` (`415` otherwise)
  and at most 8 concurrent tool calls run (`503` when busy).
- **Untrusted content**: `content_text` is untrusted third-party Markdown written by newsletter authors. Link destinations are percent-encoded
  and only http(s) links are emitted, but plain text is passed through verbatim (it can contain Markdown or HTML-like text such as
  `[a](javascript:x)`). Sanitize link schemes and raw HTML before rendering it in a browser or UI.
- `is_paywalled` is `true` for every non-public audience (`only_paid`, `founding`, `only_free`): without a subscriber cookie the API only serves a preview,
  so `content_text` of such posts is a truncated preview.
- Rate limits (`429`) and 5xx responses are retried with back-off; per-publication and per-post failures are reported in `errors`
  and never abort other publications.

### Pricing

Pay per event: **$0.001 per result-item** (`result-item`: one de-duplicated publication or post, as a dataset item or an MCP tool
result row); the `actor-start` event is free and `list_preset_publications` is free. `max_items` and `max_total_charge_usd` are hard
caps enforced in code, so a run never charges more than you configure. Invalid input and empty results are never charged.

### Related MCP Servers by Mutualistic Labs

| Actor | Covers | Store | Standby MCP URL |
|---|---|---|---|
| Multi-ATS Career Jobs Search MCP | Greenhouse, Lever, Ashby, SmartRecruiters, Workable | https://apify.com/mutualistic_housing/multi-ats-career-jobs-mcp | https://mutualistic-housing--multi-ats-career-jobs-mcp.apify.actor/mcp |
| Google Ads Transparency & Ad Spy MCP | SearchCreatives, SearchSuggestions, `content.js` ad-copy & video metadata | https://apify.com/mutualistic_housing/google-ads-transparency-mcp | https://mutualistic-housing--google-ads-transparency-mcp.apify.actor/mcp |
| Multi-Engine Keyword & Autocomplete MCP | Google, YouTube, Amazon, Bing, DuckDuckGo, Brave + `google:suggestrelevance` & search intent | https://apify.com/mutualistic_housing/keyword-autocomplete-mcp | https://mutualistic-housing--keyword-autocomplete-mcp.apify.actor/mcp |
| Discourse Forum Search & Threads MCP | community.openai.com, discuss.huggingface.co, meta.discourse.org + any public Discourse | https://apify.com/mutualistic_housing/discourse-forum-mcp | https://mutualistic-housing--discourse-forum-mcp.apify.actor/mcp |
| Google Trends Realtime & Entities MCP | i0OFE realtime trends, trending/rss news, Knowledge Graph autocomplete entities | https://apify.com/mutualistic_housing/google-trends-realtime-mcp | https://mutualistic-housing--google-trends-realtime-mcp.apify.actor/mcp |
| Substack Newsletter, Posts & Podcast MCP | Publication search, archives & within-newsletter search, full post Markdown, podcast audio URLs | https://apify.com/mutualistic_housing/substack-newsletter-mcp | https://mutualistic-housing--substack-newsletter-mcp.apify.actor/mcp |

# Actor input Schema

## `mode` (type: `string`):

archive = posts of each publication (newest or top, optional keyword search inside the newsletter); search_publications = find publications by keyword (needs query); posts = full content of explicit post URLs or slugs.

## `publications` (type: `array`):

Preset keys (pragmaticengineer, lenny, semianalysis, astralcodexten, noahpinion, slowboring, oneusefulthing, garymarcus, thezvi, simonw, importai, bytebytego, latentspace, thegeneralist, heathercoxrichardson), Substack subdomains, \*.substack.com URLs or custom newsletter domains (https only). 1 to 10 publications. Empty means pragmaticengineer. Ignored by mode search_publications.

## `query` (type: `string`):

Required for mode search_publications (up to 200 characters). In mode archive it is an optional keyword search inside each newsletter. Ignored by mode posts.

## `sort` (type: `string`):

Archive order: new = newest first, top = most popular first.

## `include_full_text` (type: `boolean`):

Fetch the full post and return it as Markdown in content_text (archive mode: only for the selected posts that lack a body in the archive). Posts mode always fetches the full post.

## `audience_filter` (type: `string`):

Archive mode: all = every post, everyone = free posts only, only_paid = paid (and founding) posts only.

## `post_urls` (type: `array`):

Mode posts: full post URLs such as https://newsletter.pragmaticengineer.com/p/some-post (1 to 50 posts in total together with slugs).

## `slugs` (type: `array`):

Mode posts: post slugs bound to the first (and only) explicitly given publication.

## `max_items` (type: `integer`):

Maximum number of result items to return (and be charged for), 1 to 500.

## `max_total_charge_usd` (type: `number`):

Hard spending cap for this run; results are truncated so the charge never exceeds it.

## Actor input object example

```json
{
  "mode": "archive",
  "publications": [
    "pragmaticengineer"
  ],
  "sort": "new",
  "include_full_text": true,
  "audience_filter": "all",
  "max_items": 25
}
```

# Actor output Schema

## `items` (type: `string`):

Dataset items: publication and post records.

# API

You can run this Actor programmatically using our API. Below are code examples in JavaScript, Python, and CLI, as well as the OpenAPI specification and MCP server setup.

## JavaScript example

```javascript
import { ApifyClient } from 'apify-client';

// Initialize the ApifyClient with your Apify API token
// Replace the '<YOUR_API_TOKEN>' with your token
const client = new ApifyClient({
    token: '<YOUR_API_TOKEN>',
});

// Prepare Actor input
const input = {
    "publications": [
        "pragmaticengineer"
    ]
};

// Run the Actor and wait for it to finish
const run = await client.actor("mutualistic_housing/substack-newsletter-mcp").call(input);

// Fetch and print Actor results from the run's dataset (if any)
console.log('Results from dataset');
console.log(`💾 Check your data here: https://console.apify.com/storage/datasets/${run.defaultDatasetId}`);
const { items } = await client.dataset(run.defaultDatasetId).listItems();
items.forEach((item) => {
    console.dir(item);
});

// 📚 Want to learn more 📖? Go to → https://docs.apify.com/api/client/js/docs

```

## Python example

```python
from apify_client import ApifyClient

# Initialize the ApifyClient with your Apify API token
# Replace '<YOUR_API_TOKEN>' with your token.
client = ApifyClient("<YOUR_API_TOKEN>")

# Prepare the Actor input
run_input = { "publications": ["pragmaticengineer"] }

# Run the Actor and wait for it to finish
run = client.actor("mutualistic_housing/substack-newsletter-mcp").call(run_input=run_input)

# Fetch and print Actor results from the run's dataset (if there are any)
print(f"💾 Check your data here: https://console.apify.com/storage/datasets/{run.default_dataset_id}")
for item in client.dataset(run.default_dataset_id).iterate_items():
    print(item)

# 📚 Want to learn more 📖? Go to → https://docs.apify.com/api/client/python/docs/quick-start

```

## CLI example

```bash
echo '{
  "publications": [
    "pragmaticengineer"
  ]
}' |
apify call mutualistic_housing/substack-newsletter-mcp --silent --output-dataset

```

## MCP server setup

```json
{
    "mcpServers": {
        "apify": {
            "type": "http",
            "url": "https://mcp.apify.com/?tools=fetch-actor-details,mutualistic_housing/substack-newsletter-mcp"
        }
    }
}
```

The hosted server signs you in with OAuth on first connect, so no API token belongs in this config. Clients without OAuth support can send an `Authorization: Bearer <APIFY_API_TOKEN>` header instead, using a token from API & Integrations in Apify Console (https://console.apify.com/settings/integrations).

## OpenAPI specification

Download the OpenAPI definition: https://api.apify.com/v2/actors/Ycuno2LVw99Oj0z4V/builds/0jmWMStePgct14t72/openapi.json