Postbye
Postbye is an AI an MCP server for AI assistants that serves subscription cancellation guides and ready-to-send cancellation letters. It gives AI agents and assistants lookup access to how companies accept cancellations, notice periods, mailing addresses and letter templates without sign-in.
About Postbye
Postbye is an AI a public MCP server that provides structured cancellation information and plain-text letters for thousands of subscriptions and memberships. The service exposes a single streamable HTTP endpoint (https://postbye.com/mcp) that returns JSON and implements four read-only MCP tools: search_companies, get_cancellation_guide, get_cancellation_letter and list_categories. The server is closed-world and read-only so clients only look things up; nothing is changed or stored by Postbye.
Clients call the endpoint with POST only; a GET returns a short description (HTTP 405) because /mcp accepts POST requests. Cross-origin calls from web clients are allowed and the server keeps no sessions or authentication tokens, so connectors in Claude, ChatGPT (developer mode), Cursor, VS Code and other agents can be added with no account or API key. The site publishes discovery files (mcp.json and a server card), a plain-text site map at /llms.txt and an official MCP Registry entry (com.postbye/postbye). The server implementation and README are available on GitHub as open source.
Capabilities MCP Streamable HTTP transport with JSON responses Four read-only tools: search_companies, get_cancellation_guide, get_cancellation_letter, list_categories Public endpoint with no authentication, CORS-enabled and sessionless
Postbye MCP server is free and public; no account, API key or sign-in is required for the read-only endpoint.
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Who is using Postbye?
Key Features
- Four read-only MCP tools: search_companies, get_cancellation_guide, get_cancellation_letter and list_categories
- Structured cancellation guides and templates covering 8,600+ subscriptions, memberships and gym contracts
- Single public endpoint (https://postbye.com/mcp) using MCP Streamable HTTP transport with JSON responses
- No authentication or sessions required; CORS-enabled for direct browser or agent calls
- Discovery files and registry entry published: mcp.json, server card, llms.txt and Official MCP Registry name com.postbye/postbye
- Open-source server code and documentation hosted on GitHub (postbye-team/postbye-mcp)
Use Cases
- Answer user questions about how to cancel a specific subscription using an AI assistant
- Generate a ready-to-send plain-text cancellation letter with the correct mailing address
- Provide verified notice periods, billing-partner notes and traps to check before cancelling
- Populate a subscription tracker or personal-finance app with cancellation instructions and sources
- Coordinate certified-mail cancellation by producing the letter and handing it to Postbye's mailing service