tidy3d-mcp 0.12.1

Local stdio FastMCP server for Tidy3D

Tidy3D MCP

A local Model Context Protocol (MCP) server that lets clients drive the Flexcompute Tidy3D viewer and consume viewer artifacts without needing a browser session.

Capabilities

• Authenticates against the remote FlexAgent MCP endpoint using your Tidy3D API key.
• Proxies viewer automation commands such as launching the viewer, rotating the camera, toggling structure visibility, running simulation health checks, and capturing screenshots.
• Returns viewer captures as MCP images so downstream tools can consume them immediately.

Requirements

• Python 3.10 or newer
• uv for dependency management
• Network access to the target FlexAgent MCP deployment (defaults to the hosted https://flexagent.dev-simulation.cloud/ endpoint)

Installation

uv sync

This resolves the project environment and installs the tidy3d-mcp console entry point.

Usage

Start the server from the project root and supply your API key (see Tidy3D installation docs for instructions to obtain it):

uv run tidy3d-mcp -- --api-key YOUR_TIDY3D_API_KEY

The server listens on stdio for MCP requests and forwards them to the remote FlexAgent server using the provided API key for authentication.

Integrating with MCP Hosts

• VS Code / Cursor: Select the "Tidy3D MCP" binary (uv run tidy3d-mcp) when configuring an stdio MCP provider.
• Custom hosts: Launch the command above and connect using the Model Context Protocol over the process stdio pipes.

Configuration

Environment variables control the server at startup:

Variable	Purpose	Default
REMOTE_MCP_URL	Target MCP endpoint to proxy.	https://flexagent.dev-simulation.cloud/

Pass --api-key whenever you launch the server. Hosts that wrap the binary must forward that argument when spawning the process.

Tools Exposed to Clients

Tool	Description
start_viewer	Launches the viewer for a simulation file and returns the resolved viewer_id.
rotate_viewer	Rotates the active viewer toward the requested direction (e.g. TOP, BOTTOM).
show_structures	Applies a boolean visibility array to the current viewer structures.
capture	Captures the current frame of the viewer.
check_simulation	Returns validation warnings or errors reported by the viewer.

Development Tips

• Run uv run ruff check to lint the project and uv run ruff format to apply formatting.
• The server relies on fastmcp.as_proxy; consult the upstream FastMCP documentation for advanced configuration such as custom authentication flows or additional transports.
• When debugging viewer interactions, inspect the returned data_url to confirm that capture payloads reach the client.

Troubleshooting

• API key rejected: Confirm the key is current by visiting the Tidy3D account page and copying a fresh key. Keys can be regenerated through the web interface if needed.
• Viewer fails to start: Verify the simulation file exists, the MCP host provides the correct working directory, and the remote FlexAgent endpoint is reachable.