Reletter

com.reletterPublished by reletter.comOfficial publisherv0.1.0Updated Oct 27, 2026

Search and analyze 7M+ newsletters, issues, contacts, and chart rankings from Reletter.

VerifiedStreamable HTTPWeb executableWeb Search & ScrapingData & AnalyticsBusiness & Commerce

Overview

AI-generated overview

Remote MCP server that lets an assistant search and analyze Reletter's index of 7M+ newsletters, issues, contacts and chart rankings.

What you can do
  • Search newsletters by topic, title or author, with keyword autocomplete and a language reference list
  • Full-text search newsletter issue bodies, list a publication's recent issues and pull a single issue's body text
  • Read publication metadata such as subscribers, engagement, socials, rankings and SEO reach
  • Retrieve email contacts, contact pages and social accounts for a newsletter
  • Browse chart platforms and categories and fetch the latest chart rankings
  • Check the API request quota and monthly usage
When to use it
Useful for media research, PR and sponsorship work: finding newsletters to pitch or partner with, building target lists with verified contacts, monitoring brand or keyword mentions, and tracking newsletter chart rankings.
Requirements
A remote endpoint at mcp.reletter.com with OAuth authentication; a Reletter API key is entered when the connector is added. No local runtime is needed for normal use. Forking or self-hosting requires Node.js and, for deployment, a Cloudflare account.
Before you install
The server returns verified contact email addresses and other newsletter data, so treat exported contacts as personal data and respect outreach and privacy rules. The README also describes an automated payment flow that buys an API key with a card token or USDC, which spends money; use it only deliberately. Quota is metered per month.

Installation

In SourceWeft

  1. Open Reletter in the dashboard and add it to a workspace.
  2. Connect the required credentials. They are stored privately and never shown on public pages.
  3. Enable the server for the chats that should use its tools.

Web executable via Streamable HTTP. Remote servers run from the web runtime once configured in a workspace.

Use with an agent

Paste this prompt into Claude Code, Codex, Cursor or another agent — or into SourceWeft chat. The agent reads this server's install guide, shows you its publisher, endpoint and sign-in, and adds it to your client once you agree. Keys never go into a command.

Read https://sourceweft.com/mcp/com.reletter%2Freletter/install.md and connect the MCP server it describes to my client. Before changing any config, show me its publisher, endpoint and sign-in method and wait for my OK. Never put an API key in a command or in a file I would commit; ask me where it should come from.

Read the install guide the agent follows

Other MCP clients

Add this to your client's mcpServers config. The client completes OAuth sign-in on first connect.

{
  "mcpServers": {
    "reletter": {
      "type": "http",
      "url": "https://mcp.reletter.com/"
    }
  }
}

README

Reletter MCP Server

Give AI agents and LLMs access to newsletter data from Reletter. Search 7M+ email newsletters across Substack, LinkedIn, Ghost, Beehiiv, and Kit. Fetch metadata, contacts, issues, and chart rankings.

This is a remote Model Context Protocol (MCP) server that connects AI assistants like Claude, ChatGPT, and Cursor to the Reletter API.

Use cases

  • Read and analyze newsletter issues — pull the full body text of any indexed issue into your AI workflow
  • Search and discover newsletters — find newsletters by topic, platform, or audience size
  • Find newsletters to pitch — get your product, tool, or book featured. Filter by audience size, topic, or platform, then pull verified contact emails in one pass
  • Build sponsorship, cross-promotion, and PR target lists — pull verified contacts and export them to your CRM
  • Monitor brand or keyword mentions — track when your brand, competitors, or clients are mentioned across newsletters
  • Track chart rankings — daily Substack / LinkedIn / Kit / Reletter chart data

Tools

  • search_publications — Search for newsletters by topic, title, or author with filters
  • search_issues — Full-text search across newsletter issue bodies
  • autocomplete — Suggested keywords and matching newsletters for a partial query
  • get_publication — Full metadata for a newsletter (subscribers, engagement, social, rankings, SEO reach)
  • list_issues — Recent issues for a publication
  • get_issue — A single issue with body text
  • contacts — Email contacts, contact pages, social accounts for a newsletter
  • chart_categories — Available chart platforms and categories
  • chart_rankings — Latest chart rankings for a platform / category
  • list_languages — Reference list of languages
  • api_quota — Your API request quota and usage for the month

Setup

You need a Reletter API key. Get one here.

For autonomous agents that want to provision a key without a human in the loop, Reletter implements the Machine Payments Protocol. Hit POST https://api.reletter.com/api/payments/buy/ to get a 402 challenge, pay with a Stripe Shared Payment Token or with USDC on Tempo, and the response carries an API key tied to a freshly-provisioned account. Current bundle tiers: GET https://api.reletter.com/api/payments/bundles/. See https://reletter.com/llms-full.txt for the full flow.

ChatGPT

  1. Go to Settings → Apps → Advanced settings and enable Developer mode
  2. Click Create app
  3. Enter Name: Reletter
  4. Enter MCP Server URL: https://mcp.reletter.com
  5. Click Create and enter your Reletter API key when prompted

Claude.ai

  1. Go to Settings → Connectors
  2. Click Add custom connector and enter name Reletter and MCP server URL https://mcp.reletter.com
  3. Click Add and enter your Reletter API key when prompted

Claude Desktop

Add to your config file and restart Claude Desktop:

  • macOS: ~/Library/Application Support/Claude/claude_desktop_config.json
  • Windows: %APPDATA%\Claude\claude_desktop_config.json
json
{  "mcpServers": {    "reletter": {      "url": "https://mcp.reletter.com"    }  }}

Claude Code

Add to your project's .mcp.json:

json
{  "mcpServers": {    "reletter": {      "type": "http",      "url": "https://mcp.reletter.com"    }  }}

Cursor

Go to Settings → MCP → Add new MCP server. Set type to URL and enter https://mcp.reletter.com.

Development

If you want to fork or customize this MCP server for your own needs, here is how you can run or deploy it.

Prerequisites

Local dev

bash
npm installnpm start

The server runs at http://localhost:8789. Test with the MCP Inspector:

bash
npx @modelcontextprotocol/inspector@latest

Type-check

bash
npm run type-check

Regenerate Cloudflare types

After changing wrangler.jsonc:

bash
npm run cf-typegen

Source: README.md at commit 2ff99d0

Tools

0
This server asks you to sign in, so SourceWeft could not read its tools without an account and has not indexed them. What a connected account sees can depend on that account and its permissions.

Version history

1
  1. v0.1.0LatestSep 16, 2026

Score

85% of the applicable checks met

How complete this listing is, computed from the registry entry, the endpoint and public sources. Not a rating of the server and not a statement that it is safe or working today: reachability is a dated check, and no installs or reviews go into the score.

  • Reached in the last 30 daysRequired25 pts
  • Auth declaredRequired10 pts
  • Tools listed15 pts

    Answer tools/list without a credential, or ship a package that starts in a sandbox without one.

  • DescriptionRequired15 pts
  • Logo10 pts
  • Documentation15 pts
  • License10 pts