Simmer — Claude Code MCP server: markets and setup
Connect an AI agent to Simmer to explore prediction markets and place trades. Use virtual $SIM to test trading before using real funds.
claude mcp add --env SIMMER_API_KEY=<SIMMER_API_KEY> --env SIMMER_MCP_ALLOW_LIVE=<SIMMER_MCP_ALLOW_LIVE> --transport stdio simmer -- npx -y simmer-mcpWhat Simmer does
Simmer is an MCP server that connects an agent to Simmer’s prediction-market API. The SDK supports browsing markets and trading; available options include virtual $SIM and venues such as Polymarket and Kalshi. The server is distributed as the simmer-mcp package.
You’ll need a Simmer API key, passed through SIMMER_API_KEY. Virtual trading lets you test without risking real funds. Real trades require live execution to be enabled; self-custody trading on Polymarket also requires WALLET_PRIVATE_KEY. Without the API key, the server cannot connect to Simmer.
What it helps with
- connect an agent to Simmer prediction markets
- browse active markets through the API
- test trading ideas with virtual currency
- place trades through a supported venue
Example prompts for the agent
- Find active Simmer markets and sort them by volume.
- Test this trading idea using virtual
$SIM. - Prepare a Polymarket trade and show me its parameters first.
How to install Simmer
Platform CLI
claude mcp add --env SIMMER_API_KEY=<SIMMER_API_KEY> --env SIMMER_MCP_ALLOW_LIVE=<SIMMER_MCP_ALLOW_LIVE> --transport stdio simmer -- npx -y simmer-mcpReplace <…> with your own values
Platform CLI
codex mcp add simmer --env SIMMER_API_KEY=<SIMMER_API_KEY> --env SIMMER_MCP_ALLOW_LIVE=<SIMMER_MCP_ALLOW_LIVE> -- npx -y simmer-mcpReplace <…> with your own values
Config file
{
"mcpServers": {
"simmer": {
"command": "npx",
"args": [
"-y",
"simmer-mcp"
],
"env": {
"SIMMER_API_KEY": "<SIMMER_API_KEY>",
"SIMMER_MCP_ALLOW_LIVE": "<SIMMER_MCP_ALLOW_LIVE>"
}
}
}
}Replace <…> with your own values
Config file
{
"servers": {
"simmer": {
"type": "stdio",
"command": "npx",
"args": [
"-y",
"simmer-mcp"
],
"env": {
"SIMMER_API_KEY": "<SIMMER_API_KEY>",
"SIMMER_MCP_ALLOW_LIVE": "<SIMMER_MCP_ALLOW_LIVE>"
}
}
}
}Replace <…> with your own values
Platform CLI
gemini mcp add -e SIMMER_API_KEY=<SIMMER_API_KEY> -e SIMMER_MCP_ALLOW_LIVE=<SIMMER_MCP_ALLOW_LIVE> simmer npx -y simmer-mcpReplace <…> with your own values
Step by step, with commands for each platform: How to add an MCP server to Claude Code, Codex, Cursor, VS Code, Gemini CLI and more
Questions about Simmer
How do I install Simmer in Claude Code?
Run claude mcp add simmer-mcp -e SIMMER_API_KEY=<SIMMER_API_KEY> -- npx -y simmer-mcp, replacing the placeholder with your API key.
What does Simmer do?
It connects an agent to Simmer’s prediction-market API. The SDK supports market browsing and trading, including with virtual currency.
Can I test trades without real funds?
Yes. Simmer supports trading with virtual $SIM; the SDK also describes simulated trades using real market prices with live=False.
