Open-source Mattermost MCP alternatives
The Mattermost MCP server is open source, which fits a chat platform that teams often run themselves. You can read how it works with channels, messages, threads, and files before wiring it in. The reason to compare against the open-source servers below is usually that your chat lives elsewhere, and you still want code you can audit before an agent posts.
Each option here publishes its source. You can read which calls it makes, pin a version, and patch behaviour yourself, which matters for any tool that can send messages to a team.
The 8 best open-source alternatives
Built on Telethon and fully open source, the Telegram server reads chats, manages groups and contacts, and sends or modifies messages and media. The repo shows exactly what an agent can do in an account.
Set up Telegram →Pushes or broadcasts text and flex messages, manages rich menus, and reads profiles, with its source published. Reading the code confirms what it can broadcast to an audience.
Set up LINE →Open source and aimed at Matrix homeservers, it reads rooms and messages, sends chats, and manages rooms over OAuth. Federated chat you can inspect, close in spirit to a self-run Mattermost.
Set up Matrix →Reads and posts messages for Rocket.Chat while managing threads, DMs, files, reactions, and pins, all open source. The nearest like-for-like, with code you can vet.
Set up Rocket.Chat →- TwilioOfficial
Twilio's official server is open source and exposes SMS, voice, Verify, Lookup, and 1,400+ endpoints. Auditing it matters because it places real calls and sends real messages.
Set up Twilio → - VonageOfficial
Open source and multichannel, Vonage sends SMS, WhatsApp, RCS, and voice, manages numbers, and pulls reports. The repo lets you check which channels an agent can reach.
Set up Vonage → - Discord MCPCommunity
This open-source community server runs a Discord bot across messages, channels, forums, roles, and webhooks. Reading the source before granting bot permissions is straightforward.
Set up Discord MCP → Notion's server is open source but aimed at a workspace, not chat: search, read, and write pages and databases. Include it only if the messages you sent in Mattermost were really publishing content into docs.
Set up Notion →
How to choose
Every pick publishes its code, including Mattermost itself, so the choice is about platform rather than auditability. Rocket.Chat is the closest open peer as another self-hostable team-chat product, with Matrix the federated option. Telegram and Discord swap to consumer networks, Twilio and Vonage reach phones, and LINE broadcasts to an audience. Read the repo before handing any of them send or post access.
FAQ
- Is the Mattermost MCP server open source?
- Yes. The Mattermost server is a community, open-source project, so you can read how it works with channels, messages, threads, and files. The alternatives on this page are open source too, which lets you compare implementations directly.
- Why pick an open-source chat MCP server?
- You can read exactly which send and read calls the server can make, pin or patch the version you run, and keep credentials on infrastructure you control. That matters most for tools that post to team channels or message real people.