MCP Servers

Model Context Protocol (MCP) is an open protocol for exposing tools and resources from external processes to an AI agent. Ghast is a first-class MCP client — you can connect any MCP-compatible server and its tools immediately become available in the composer's tool toggle.

What you can connect

Two configuration styles:

Stdio servers (local subprocess)

A command the desktop client spawns as a subprocess; communication is over stdin/stdout.

json

{
  "servers": {
    "postgres": {
      "command": "/usr/local/bin/postgres-mcp",
      "args": ["--db", "production"],
      "env": { "PGPASSWORD": "$KEYCHAIN:postgres" }
    }
  }
}

Best for local tooling — file-system, database, internal CLIs, custom shims.

URL servers (HTTP-based)

Remote MCP servers reached over HTTPS, with one of three transports:

Transport	When it's used
SSE	Older HTTP-based MCP servers with Server-Sent Events
Streamable HTTP	Newer MCP servers using chunked HTTP streaming
Plain HTTP	Simple request/response MCP endpoints

json

{
  "servers": {
    "remote-api": {
      "url": "https://mcp.example.com/api",
      "headers": { "Authorization": "Bearer $VAULT:my-token" }
    }
  }
}

Setting up a server

Open Settings → MCP.
Click Add Server and pick stdio or URL.
Fill in the command / URL and any auth headers or env vars.
Test connection. Ghast performs an initialize handshake and lists discovered tools.
Save. The server is now active.

If the server requires OAuth (some hosted MCPs do):

Click Connect to open the OAuth flow in a system browser.
Authorise in the third-party UI.
Return to Ghast — the OAuth token is captured automatically and stored in the Profile Vault.

How tools appear in the composer

Once a server is connected:

Its tools appear in the composer's tool toggle as <servername>__<toolname>.
The agent can call them like any built-in tool.
Results are rendered as collapsible cards in the chat.

You can toggle individual tools on/off per turn, or set defaults in Settings → MCP.

Resources

MCP also supports resources — read-only blobs the server makes available (files, docs, dashboards). Resources from connected servers can be referenced in chat via the @ mention picker, and the agent can read them as context.

Removing or rotating a server

Action	Effect
Disable	Tools and resources are hidden in the composer; subprocess keeps running until next restart
Remove	Subprocess killed, tools removed, server entry deleted
Rotate auth	Edit the env var or header value and reconnect

OAuth tokens issued via Ghast's OAuth flow can be revoked from the third-party server's side; the next call will fail and prompt re-auth.

Security notes

MCP servers run with the same privileges as the desktop app (no extra sandbox).
An stdio server is a subprocess; assess its trust like you would any local binary.
A URL server sees only what the agent sends in tool calls. It does not have access to your memories or wallet.
OAuth tokens, like other secrets, sit encrypted in the Profile Vault.

See Security: Local Execution Boundary (covered in security pages) for the full model.

MCP Servers ​

What you can connect ​

Stdio servers (local subprocess) ​

URL servers (HTTP-based) ​

Setting up a server ​

How tools appear in the composer ​

Resources ​

Removing or rotating a server ​

Security notes ​

Related pages ​