Universal Modder: fix fal key and MCP connection problems

Decide whether you need cloud assets yet

fal is used for cloud-generated assets. Start with placeholder art and a small code change if you do not need generated images, meshes or sound yet. Do not buy credits just to diagnose a local CLI installation.

The README also documents um comfy for images from a local ComfyUI server. That route needs a working local server; it is not a promise of free cloud generation.

Check that the agent sees FAL_KEY without printing it

The project uses the environment variable FAL_KEY. A variable set in one terminal is not necessarily available to an editor launched earlier or to a separate WSL environment.

Check only whether the variable exists. The commands below do not print its value. After configuring it in your local environment, restart the agent from that environment and retry the presence check there.

On macOS or Linux, use the first command. On Windows PowerShell, use the second. Missing here means the process cannot see the variable; present does not prove that the key is valid.

[ -n "$FAL_KEY" ] && echo "FAL_KEY is present" || echo "FAL_KEY is missing"

if ($env:FAL_KEY) { "FAL_KEY is present" } else { "FAL_KEY is missing" }

Check the configuration for the agent you actually use

The repository’s .mcp.json points to https://mcp.fal.ai/mcp and supplies an Authorization header using Bearer plus the FAL_KEY environment variable. Other integrations have their own configuration files, including .codex/config.toml, .cursor/mcp.json, .vscode/mcp.json and opencode.json.

Review the matching file in the official repository. Do not paste a Claude Code JSON configuration into a TOML-based agent configuration. If a plugin manages the connection, inspect that plugin’s MCP status before adding another copy of the server.

The um fal CLI and an agent’s MCP server connect through different paths. Diagnose the failed path rather than treating success in one as proof that both are ready.

Keep authentication and generation errors separate

Record which tool failed, the exact status code and a redacted error message. An authentication failure, a network timeout and a generation request rejected for its parameters need different fixes.

If the provider reports account or billing restrictions, check the fal dashboard before retrying. Repeated generation requests can have costs; a connection check is not permission for an unlimited paid run.

Before sharing a log, remove authorization headers, API keys and private local paths. Never enter a real key into this website or include one in a generated mod brief.

Verify one small result, then return to the mod

First verify tool availability with the help command. Check the agent’s MCP status separately. If you intentionally use a paid cloud generation, set a spending limit and request only a small asset you can inspect.

An asset returned by the provider is not yet a working game asset. Check transparency, dimensions and the loader’s expected format, then test it in your actual game. ModLab has not reproduced this cloud-to-game flow in-game.

um fal --help
um comfy --help