Simmer MCP Setup

One-shot bootstrap that wires the Simmer MCP server into your agent runtime. Read-once, run-once — after this completes, the skill itself isn't needed again.

What the Simmer MCP is (and isn't)

The Simmer MCP gives your agent a catalog of pre-built Simmer trading skills it can invoke as tools — strategies like polymarket_copytrading, polymarket_fast_loop, kalshi_weather_trader, etc. — plus utility tools (skill discovery, error troubleshooting).

What this MCP is for: running pre-baked Simmer trading strategies through your agent. Ask "run the polymarket_copytrading skill on the top 3 markets in dry-run mode" and Claude Code (or Cursor / OpenClaw / etc.) invokes it. Each skill runs as a subprocess that calls the Simmer API. Real trades land on the configured venue — paper sim by default, real venues require an explicit triple opt-in (dry_run=false + trading_venue=polymarket|kalshi + SIMMER_MCP_ALLOW_LIVE=true env var on the MCP server).

What this MCP doesn't do (yet): expose raw trade primitives like place_order or get_briefing as standalone tools. Ad-hoc operations like "buy $10 yes on this BTC market" or "show me my current portfolio" aren't possible through MCP today — those still need the Python SDK, which exposes client.trade(), client.get_briefing(), etc. directly. Raw MCP primitives are a tracked follow-up.

So: MCP and SDK are different shapes, both legitimate. MCP runs pre-built strategies through your agent with safety defaults; SDK builds custom logic with full primitive access.

What you'll have at the end

• simmer-mcp runnable via npx -y simmer-mcp (global install optional)
• Your agent runtime's MCP config updated with a simmer entry
• SIMMER_API_KEY plumbed into the MCP subprocess
• Simmer tools visible to your agent:
  • 3 free utility tools (always available): list_skills, get_skill_docs, troubleshoot_error
  • A catalog of per-skill execution tools — one tool per bundled Simmer trading skill (Polymarket strategies, Kalshi weather trading, sentiment/copytrading skills, plus utilities like preflight). The catalog grows over time — call list_skills to see what's currently available, or browse the live catalog at clawhub.ai/skills?q=simmer.
  • 4 Pro-gated autoresearch tools (init_experiment, run_experiment, log_experiment, backtest_experiment) — only registered if you're on the Pro plan.

Step 1 — confirm you have an API key

This skill needs SIMMER_API_KEY to wire into the MCP config. Three cases:

Case A — key already in env. Verify:

[[ "$SIMMER_API_KEY" == sk_live_* ]] && echo "OK" || echo "MISSING or malformed"

If "OK", skip to Step 2.

Case B — key from prior dashboard registration. Get it from simmer.markets/dashboard → your agent → API key tab. Paste it in (don't pipe from clipboard — pastes can pick up trailing characters):

read -s -p 'SIMMER_API_KEY: ' KEY && export SIMMER_API_KEY=$KEY

Case C — no agent registered yet. Register one now:

curl -X POST https://api.simmer.markets/api/sdk/agents/register \
  -H "Content-Type: application/json" \
  -d '{"name": "my-agent", "description": "What this agent does"}'

Response includes api_key and claim_url. Save the API key:

export SIMMER_API_KEY="sk_live_..."

Send the claim_url to the human user — they need to visit it before any real-money trading is unlocked. Until then, all trades stay on the sim paper venue (this is intentional, not a bug).

Step 2 — confirm Node.js and npm are installed

The simmer-mcp server runs on Node.js. Check:

node --version  # need v18 or higher
npm --version

If both return a version → skip to Step 3.

If command not found, the user needs to install Node.js. Don't auto-install via curl | sh — it modifies the user's system without their approval. Instead, show them the platform-specific option:

The Node.js installer bundles npm, so installing Node.js gives you both. After install, the user needs to reopen their terminal so node/npm land on PATH, then re-run this step.

Why not nvm? nvm is great for developers who switch Node versions across projects. For a one-time global install of a CLI tool like simmer-mcp, the official installer is simpler.

Step 3 — install simmer-mcp (optional but recommended)

npm install -g simmer-mcp

This step is optional. The MCP config in Step 4 uses npx -y simmer-mcp, which fetches the package on first launch even without a global install. Installing globally just makes the first launch slightly faster (no fetch delay). If you skip Step 3, everything still works.

If you do install it and get an EACCES permission error on Linux/macOS: do NOT sudo npm install (creates permission tangles later). Either fix npm's global directory permissions per npm's docs, or just skip the global install — the npx -y simmer-mcp form in the config works either way.

Why no --version check? simmer-mcp's binary doesn't have CLI flags — every invocation starts the stdio MCP server. Verification happens in Step 6 when your agent calls a simmer tool and gets a real response.

Step 4 — wire up the MCP config

Detect which runtime your agent is in, then write the right config. Pattern is "use the native CLI if the runtime has one; fall back to direct config-file write."

Claude Code

Decide scope first:

Most onboarding flows want user scope — install once, available everywhere.

Preferred (no file editing):

claude mcp add -s user simmer -e SIMMER_API_KEY="$SIMMER_API_KEY" -- npx -y simmer-mcp

⚠️ Flag order matters: -e KEY=value goes after the server name simmer, then --, then the command. The example in claude mcp add --help puts -e before the name; that form fails because -e is variadic and greedily consumes the server name as an env var. The order shown here is the form that actually works in current Claude Code versions (verified on Claude Code via real add/remove cycle).

This writes ~/.claude.json for you with the correct command/args/env structure. The "$SIMMER_API_KEY" expansion bakes the literal key value into the config (MCP runtimes don't expand shell vars at server-launch time).

Fallback (if claude mcp add isn't available in this Claude Code version): add the following to ~/.claude.json under mcpServers (create the key if it doesn't exist) — use the literal API key value, not $VAR:

{
  "mcpServers": {
    "simmer": {
      "command": "npx",
      "args": ["-y", "simmer-mcp"],
      "env": {
        "SIMMER_API_KEY": "sk_live_..."
      }
    }
  }
}

For project scope instead: use the same JSON shape but write it to .mcp.json in the project root (single top-level mcpServers key, no other fields).

Cursor

Edit ~/.cursor/mcp.json (create the file if it doesn't exist):

{
  "mcpServers": {
    "simmer": {
      "command": "npx",
      "args": ["-y", "simmer-mcp"],
      "env": {
        "SIMMER_API_KEY": "sk_live_..."
      }
    }
  }
}

Project-scoped: use .cursor/mcp.json in the project root.

OpenClaw

Edit ~/.openclaw/openclaw.json and add simmer under mcp.servers:

{
  "mcp": {
    "servers": {
      "simmer": {
        "command": "npx",
        "args": ["-y", "simmer-mcp"],
        "env": {
          "SIMMER_API_KEY": "sk_live_..."
        }
      }
    }
  }
}

Restart your OpenClaw runtime so it picks up the new server.

Hermes

Hermes uses YAML, not JSON. Edit ~/.hermes/config.yaml and add under mcp_servers (snake_case — different from the other runtimes):

mcp_servers:
  simmer:
    command: "npx"
    args: ["-y", "simmer-mcp"]
    env:
      SIMMER_API_KEY: "sk_live_..."
    enabled: true

Codex

The canonical Codex MCP config path varies by install — consult Codex's MCP docs for the exact file. The block to add is the standard MCP shape:

{
  "mcpServers": {
    "simmer": {
      "command": "npx",
      "args": ["-y", "simmer-mcp"],
      "env": {
        "SIMMER_API_KEY": "sk_live_..."
      }
    }
  }
}

Other / unknown runtime

If you're on a runtime not listed above but it speaks MCP, you almost certainly need this exact block in its MCP-server config file (check the runtime's docs for where that lives):

{
  "mcpServers": {
    "simmer": {
      "command": "npx",
      "args": ["-y", "simmer-mcp"],
      "env": {
        "SIMMER_API_KEY": "sk_live_..."
      }
    }
  }
}

Step 5 — restart the runtime

MCP servers are loaded at startup. Quit and reopen your agent runtime so it picks up the new simmer entry. Some runtimes (OpenClaw, Hermes daemon mode) have a reload command — use that instead of a full restart if available.

Step 6 — verify

Don't trust "looks installed" — verify with a real tool call.

Ask your agent:

What simmer tools can you see? List them.

The agent should respond with the 3 utility tools plus per-skill execution tools:

• list_skills
• get_skill_docs
• troubleshoot_error
• A catalog of per-skill execution tools (one per bundled Simmer trading skill). The exact count depends on how many skills are currently bundled — have the agent call list_skills for the up-to-date inventory.

Then ask the agent to do something safe that exercises the API:

Use the simmer tools to show me a few of the most active markets on the sim venue.

The sim venue is paper money — no real funds at risk. If this returns market data, the handshake works end-to-end and Simmer is ready to use.

Troubleshooting

Agent says "no simmer tools available" after restart.

• Confirm the runtime fully restarted (not just reloaded the conversation).
• Check the config file actually got written — cat ~/.claude.json (or equivalent) and look for the simmer entry under mcpServers.
• For Claude Code: claude mcp list shows registered servers and their status.

Tools listed but API calls return 401.

• SIMMER_API_KEY env didn't make it into the MCP subprocess. The env block in the config has to be a direct value, not a $VAR reference — most MCP clients don't expand shell vars at server-launch time.
• Verify the key value: printenv SIMMER_API_KEY | cut -c1-20 — must start with sk_live_. A common silent failure: install commands that use pbpaste or clipboard-read primitives can write the install command text itself as the key value when the user copies the command after copying the key. Fix: get a fresh key from simmer.markets/dashboard, then export SIMMER_API_KEY="sk_live_..." typed/pasted directly.

npm install -g simmer-mcp fails with EACCES on Linux/macOS.

• Don't sudo npm install — that creates permission problems later. Either fix npm's global directory permissions per npm's docs, or just use the npx -y simmer-mcp form in your config (no global install needed; npx fetches on first launch).

claude mcp add fails with "command not found".

• Older Claude Code versions don't have the mcp add subcommand. Use the JSON-write fallback under Step 4 — Claude Code.

Tools work for list_skills but not for trading.

• Trading tools require both SIMMER_API_KEY and (for real-money venues) wallet linking. If the user wants real-money trading, they also need simmer-wallet-setup — that's a separate skill. Trading on the sim venue works without wallet setup.

Anti-patterns

• Don't auto-install Node.js via curl | sh — modifying the user's system without explicit approval is bad practice. Show the platform-specific install hint and let the user decide.
• Don't paste the API key from clipboard into a pipe. Use read -s (per SIM-2118).
• Don't sudo npm install -g. Fix the underlying npm permissions, or use npx -y simmer-mcp in the config (no global install needed).
• Don't tell the user "it should work now" without verifying. Run Step 6 — confirm a real tool call returns real data.

Links

• simmer-mcp package: npmjs.com/package/simmer-mcp
• General Simmer skill (Python SDK path): clawhub.ai/skills/simmer
• Wallet setup (real-money trading): clawhub.ai/skills/simmer-wallet-setup
• Full Simmer docs: docs.simmer.markets
• Dashboard: simmer.markets/dashboard