How to use the Add Mattermost Channel agent skill

What the add-mattermost skill makes the agent do

An agent skill is a folder of instructions and helper scripts that an AI agent can follow for one specific job. This skill walks the agent through connecting NanoClaw to a Mattermost server. Once connected, the agent can receive and send messages in Mattermost DMs, channels and threads, plus files, reactions and interactive approval cards. Messages arrive over Mattermost's WebSocket, and card clicks return to NanoClaw over an authenticated HTTP callback.

The skill is designed to be safe to re-run. Each step can be repeated without breaking an existing setup.

• Receive and send messages in Mattermost DMs, channels and threads
• Post interactive approval buttons, which return to NanoClaw through an authenticated callback
• Check the server's public configuration to confirm the settings it changed

Install the add-mattermost skill

Download the skill ZIP from this page and unzip it. You can install it in one of two places. For a personal setup, unzip it into ~/.claude/skills/. For a single project, unzip it into that project's .claude/skills/ folder.

If you use the Claude apps instead, open Settings, go to Capabilities, then Skills, and upload the skill there.

Installing the skill only makes its instructions available. The setup itself runs when you ask the agent to add Mattermost, as described below.

• Personal use: ~/.claude/skills/
• Single project: the project's .claude/skills/ folder
• Claude apps: Settings → Capabilities → Skills, then upload

Prepare the Mattermost server and NanoClaw

The skill connects to a Mattermost server. It does not install, upgrade, back up or run one. If you already run a Mattermost server, the skill will try to reuse it. If you do not have one, the skill points you to Mattermost's official guides: the Quick Start Evaluation for a temporary local trial, and the server deployment guide for a persistent or production installation.

NanoClaw must already be installed with its .env file and setup helpers. Node.js is required, since setup already needs it. You will also need a running Mattermost server URL, a Mattermost bot token, and System Admin access if the server's SiteURL has to change. mmctl and Docker are optional, and are used only for local server configuration.

• Node.js (already required by NanoClaw setup)
• NanoClaw installed with its .env and setup helpers
• A running Mattermost server URL
• System Admin access if SiteURL must be changed
• Optional: mmctl and/or Docker for local configuration
• A Mattermost bot token (the skill checks its format before saving)

Ask the agent to add Mattermost

Start a session in NanoClaw and ask in plain language. For example: add a Mattermost channel, or connect NanoClaw to my Mattermost server. The agent then follows the skill in order.

First it looks for a Mattermost server you already run, checking the MATTERMOST_BASE_URL setting, the standard local addresses, and Docker containers. It does not pick one for you. If it finds a healthy server, it shows the address and asks you to enter use to use it, or enter to give a different URL. A detected server is only a suggestion until you confirm it.

The agent does not print tokens or dump whole environment files while it works.

• Enter use to connect to the server it found
• Enter enter to type a different Mattermost URL, including the scheme such as https://
• If nothing is found, the agent gives you Mattermost's official guidance and asks for the URL once the server is running

Check the SiteURL and WebsocketURL settings

Mattermost Desktop sends its configured server URL as the WebSocket Origin. The skill therefore asks you to set the SiteURL setting to the exact same address as the one NanoClaw uses, and to keep WebsocketURL blank. The skill will not change AllowCorsFrom to fix an Origin error.

If the agent can reach your server's configuration with mmctl on the host or inside a local container, it asks before making the change. You enter set to apply the two settings, or already if they are correct. If it cannot reach local configuration, it gives you the exact mmctl commands or the System Console → Environment → Web Server path to make the change yourself, then asks you to enter ready.

To verify, the skill reads the server's public client configuration. The check should print the base URL followed by a blank line.

• Set ServiceSettings.SiteURL to the base URL NanoClaw uses
• Keep ServiceSettings.WebsocketURL blank
• Do not change ServiceSettings.AllowCorsFrom to correct an Origin error

Copy the channel files and register the channel

The skill copies the Mattermost adapter and its registration test from the channels branch of NanoClaw, then adds one import line to src/channels/index.ts. Existing files are kept during installation. If you have an older installation, the skill says to run /update-skills first so Mattermost is refreshed before you rerun it.

The skill also removes the unscoped chat-adapter-mattermost package if it is installed. The source says nothing in the repository imports it and that its name looks like a typosquat of the scoped package, so it is treated as unwanted.

• Adapter and registration test are copied from the channels branch
• One import line is appended to src/channels/index.ts, skipped if already present
• On older installs, run /update-skills before rerunning the skill

Safety notes: scripts and network access

This skill runs scripts and uses the network. Its helper scripts probe Mattermost URLs, read the server's configuration, and may run mmctl or Docker commands against a live server. These changes are made only after you approve them. The skill does not start or recreate a stopped Mattermost container without your approval.

Read the prompts before you enter set or ready. If you do not want an agent changing server settings, use the manual path the skill offers and make the change yourself. To remove the integration, the separate REMOVE.md guide lists the files, credentials and dependencies to clean up.

• Runs scripts and uses the network
• Asks before changing any server setting, and before starting a stopped container
• Removal steps are documented in REMOVE.md