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Memory Crystal reads configuration from environment variables. Which variables you need depends on your setup — cloud users only need an API key, while self-hosted deployments require a few more.

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Cloud setup

If you’re using the hosted Memory Crystal service at memorycrystal.ai, you only need one variable:
VariableDescriptionRequiredExample
MEMORY_CRYSTAL_API_KEYYour API key from the Memory Crystal dashboard. Also accepted as CRYSTAL_API_KEY.Yesmck_abc123...
Get your API key from the Memory Crystal dashboard.

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Full variable reference

VariableDescriptionRequiredExample
MEMORY_CRYSTAL_API_KEYAPI key from the dashboard. Also accepted as CRYSTAL_API_KEY.Yes (cloud)mck_abc123...
MEMORY_CRYSTAL_API_URLYour Memory Crystal backend URL. Also accepted as MEMORY_CRYSTAL_BACKEND_URL or CRYSTAL_BASE_URL.Yes (self-hosted)https://your-project-123.convex.site
CONVEX_URLSame as MEMORY_CRYSTAL_API_URL. Used by the OpenClaw plugin.Yes (plugin)https://your-project-123.convex.site
CONVEX_DEPLOYMENTYour Convex deployment identifier. Only required for self-hosted deployments.Self-hosted onlyprod:your-project-123
Cloud users only need MEMORY_CRYSTAL_API_KEY. The plugin and MCP server default to the hosted backend, so no URL configuration is required.

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Where to set variables

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MCP server

Set variables in your shell environment or in the env block of your MCP config: 
{
  "mcpServers": {
    "memory-crystal": {
      "command": "crystal-mcp",
      "env": {
        "MEMORY_CRYSTAL_API_KEY": "your-api-key-here",
        "MEMORY_CRYSTAL_API_URL": "https://your-deployment.convex.site"
      }
    }
  }
}

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OpenClaw plugin

Set variables in your shell environment, or in mcp-server/.env in the Memory Crystal repo directory. The plugin reads from the process environment at startup.

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Self-hosted deployments

For self-hosted setups, set CONVEX_URL and CONVEX_DEPLOYMENT in your shell and in mcp-server/.env: 
CONVEX_URL=https://your-project-123.convex.site
CONVEX_DEPLOYMENT=prod:your-project-123
MEMORY_CRYSTAL_API_KEY=your-api-key-here
If you don’t set CONVEX_DEPLOYMENT and CONVEX_URL, Memory Crystal falls back to the hosted cloud backend. Your data will not stay on your own infrastructure.