This guide walks through connecting MCP tool servers to simse, verifying the connection, and understanding how tool permissions work. Examples use TUI slash commands -- for headless mode, see the commands reference.
Add a tool server entry to ~/.config/simse/mcp.json (macOS / Linux) or %APPDATA%\simse\mcp.json (Windows):
{
"servers": [
{
"name": "<name>",
"transport": "stdio",
"command": "<command>",
"args": ["<arg1>", "<arg2>"]
}
]
}The name field sets a unique identifier for this tool server. You will use this name to manage the connection.
Tool server entries in mcp.json run as a subprocess: use "transport": "stdio" and provide the command that starts the server. The command field is a single executable; all arguments go in args:
{
"servers": [
{
"name": "filesystem",
"transport": "stdio",
"command": "npx",
"args": ["@modelcontextprotocol/server-filesystem", "/path/to/project"]
}
]
}simse starts the server process and communicates over its stdin/stdout. The process is managed by simse -- it starts when needed and restarts on failure.
After adding a tool, restart simse and verify the connection with simse mcp status or /mcp in the TUI. A healthy server shows as "connected" with a count of available tools.
The @modelcontextprotocol/server-filesystem package is a reference MCP implementation that exposes file read/write operations. Install it and connect it to simse:
npm install -g @modelcontextprotocol/server-filesystemThen add it to mcp.json:
{
"servers": [
{
"name": "project-files",
"transport": "stdio",
"command": "npx",
"args": ["@modelcontextprotocol/server-filesystem", "/path/to/your/project"]
}
]
}Restart simse and verify with simse mcp status.
During sessions, simse can now read and write files in your project directory.
Every tool invocation goes through permission checking before execution. The configured permission mode determines whether simse asks you for approval.
Permission modes:
| Mode | Behavior |
|---|---|
"default" | Ask before each tool invocation |
"acceptEdits" | Auto-approve file edits, ask for other actions |
"plan" | Show what tools would do, but do not execute |
"dontAsk" | Auto-approve all actions without prompting |
Cycle the permission mode during a session with the /permissions command.
Per-session permission grants:
During a session, when simse asks for permission, you can respond with:
To remove a tool, delete its server entry from mcp.json and restart simse.
To restart tool servers (useful if a server process has crashed), run simse mcp restart or /mcp restart from the TUI.
To update a tool's configuration, edit its entry in mcp.json and restart simse.