MCP Server

Phon can run an embedded Model Context Protocol (MCP) server that exposes Schwa's AI tools to external MCP clients such as Claude Code, Claude Desktop, Cursor, VS Code, Gemini CLI, and OpenCode. A connected client can read and edit open sessions, run queries and analyses, work with media and speech analysis, and test phonex expressions in the running Phon application.

The server accepts connections from this computer only (address 127.0.0.1), and every request must include an access token. It is separate from Schwa's own outbound MCP connections, which are configured with Edit MCP configuration... in the Schwa menu.

Warning:

A connected client controls Phon with the same abilities as the Schwa Edit mode, including making changes to session data. Review changes made by external tools and use Undo when a change is not correct.

Start and stop the server

The server does not run by default. Start or stop it in either of these places:

In a Session Editor, select Schwa > MCP Server > Start MCP server or Stop MCP server.
On the Schwa Preferences tab, use the Server Control row under MCP Server. The status line shows the endpoint URL while the server is running.

Enable Start MCP server with Phon to start the server automatically when the application launches. The server listens on the configured Port (default 8357); a port change takes effect the next time the server starts. If the port is already in use, the server reports the failure and remains stopped.

Access token

Requests are authenticated with a bearer token that Phon generates automatically. The Access Token row on the Schwa Preferences tab shows the token with Copy and Regenerate buttons. Regenerating invalidates configured clients, which must be updated with the new token; a running server keeps the old token until it is restarted.

Connect an external client

Select Schwa > MCP Server > Connection instructions..., or Connection instructions... on the Schwa Preferences tab, to open the Connect to Phon MCP Server dialog. Each tab holds setup instructions and a copyable configuration snippet for one client: Claude Code, Claude Desktop, Cursor, VS Code, Gemini CLI, and OpenCode. Snippets already include the endpoint URL and the current access token.

For any other client, the Other clients tab lists the values to enter manually: the Streamable HTTP transport, the endpoint URL, and the Authorization header.

Tools and session targeting

The server publishes Schwa's tool set: documentation search, project and session inspection, phonex compilation and testing, record reading and editing, find and replace, queries, analyses, media and speech analysis, and timeline actions.

Most tools operate on a session editor window open in Phon. The list_open_editors tool lists open editors with an id (#1, #2, ...) and a corpus/session path. Other tools accept either form in an optional session parameter; when it is omitted, the focused (or only open) session editor is used.

Changes made through the server are grouped into single undoable edits in the target editor's Edit > Undo history. A tool call that runs longer than two minutes is cancelled and reported to the client as an error.