Neumann: Monte Carlo simulation in your AI chat

1. 1Pick your assistant below and open its MCP connector settings. No sign-up needed to start.
2. 2Add the server URL: https://neumann.kromatic.com/mcpCopy URL
3. 3Ask your first question — try the prompt below.

claude mcp add --transport http neumann https://neumann.kromatic.com/mcp

{
  "mcpServers": {
    "neumann": {
      "url": "https://neumann.kromatic.com/mcp"
    }
  }
}

{
  "servers": {
    "neumann": {
      "type": "http",
      "url": "https://neumann.kromatic.com/mcp"
    }
  }
}

{
  "mcpServers": {
    "neumann": {
      "httpUrl": "https://neumann.kromatic.com/mcp"
    }
  }
}

Please add an MCP server named "neumann" at https://neumann.kromatic.com/mcp using the streamable HTTP transport, then confirm it's connected.

Simulate revenue = units × price where units ~ normal(mean 1000, sd 150) and price ~ triangular(18, 25, 40); run 5,000 trials and report p10/p50/p90 and the top sensitivity.

What Neumann is for

Use Neumann when a plan depends on several uncertain quantities at once and you want to know the shape of the outcome rather than a single best guess: revenue under uncertain demand and price, runway under uncertain burn, delivery dates under uncertain task durations. You supply root nodes (each an input drawn from a distribution), calc nodes (formulas over the values flowing into them), and edges naming those flows; Neumann samples the roots thousands of times and reports percentiles and summary statistics for every node.

Fermi and Neumann compose: ask Fermi for a calibrated range for each uncertain input, then hand those ranges to Neumann as root nodes to see what they imply together.

MCP endpoint

MCP-native clients connect to the Streamable HTTP transport at:

https://neumann.kromatic.com/mcp

With Claude Code, that is a single command:

claude mcp add neumann --transport http https://neumann.kromatic.com/mcp

Every tool also has a plain HTTP twin for clients that do not speak MCP: GET https://neumann.kromatic.com/mcp/tools lists them and POST https://neumann.kromatic.com/mcp/tools/<name> calls one. Simulations can additionally be submitted to POST https://neumann.kromatic.com/api/v1/runs, which supports streaming progress for long runs.

Authentication — API key or opaque bearer token

Create an account with a single unauthenticated POST — no body, no browser, no human approval:

curl -X POST https://neumann.kromatic.com/api/v1/accounts

The 201 response carries account_id, api_key, credit_balance and created_at.

Opaque tokens are minted by POST https://neumann.kromatic.com/api/v1/tokens and shown in plaintext exactly once; Neumann stores only a hash. Use one when your MCP client can set an Authorization header but cannot pass a per-call argument.

Anonymous access

Sending no credentials at all works for a limited trial — see the free tier above for the exact daily run, trial and node caps. It exists so you can try Neumann before signing up, not as a way to run an integration — create an account for anything beyond a first look (and to get the signup credit grant).

Available tools

check_simulation_model and estimate_simulation_size_and_cost are free, so the cheap way to work is to check the model, estimate the cost, and only then run.

The live tool descriptors, including the full argument schemas, are served by Neumann itself at https://neumann.kromatic.com/mcp/tools. Treat that endpoint as authoritative if it ever disagrees with this table.

Worked example

Monthly revenue from an uncertain number of units sold at an uncertain price, over 1,000 trials. This uses the plain HTTP twin of run_monte_carlo_simulation, which is the easiest way to see the request and response shape:

curl -X POST https://neumann.kromatic.com/mcp/tools/run_monte_carlo_simulation \
  -H "Content-Type: application/json" \
  -d '{
  "graph": {
    "contract_version": "1.0",
    "root_nodes": [
      {
        "id": "units_sold",
        "name": "Units sold per month",
        "distribution_type": "normal",
        "distribution_params": {
          "mean": 1000,
          "std": 150
        }
      },
      {
        "id": "price_per_unit",
        "name": "Price per unit (USD)",
        "distribution_type": "triangle",
        "distribution_params": {
          "min_val": 18,
          "mode_val": 25,
          "max_val": 40
        }
      }
    ],
    "calc_nodes": [
      {
        "id": "revenue",
        "name": "Monthly revenue (USD)",
        "formula": "{e_units} * {e_price}"
      }
    ],
    "edges": [
      {
        "id": "e_units",
        "source": "units_sold",
        "target": "revenue"
      },
      {
        "id": "e_price",
        "source": "price_per_unit",
        "target": "revenue"
      }
    ],
    "run_params": {
      "trials": 1000,
      "time_periods": 1
    }
  },
  "seed": 42
}'

This call carries no credentials, so it uses the free anonymous tier (up to 1,000 trials per run). With an account, add -H "X-API-Key: <your api_key>" and raise trials as high as you need. A run this small comes back inline, with a run_id, a completed status, the run tier and the credits debited, plus per-node results: percentiles (p10, p50, p90) and basic_stats (mean, std, min, max) for each node and time period. Passing a seed makes the run reproducible.

Credits and access

Neumann is a paid, per-credit product. A new account starts with a grant of free credits so you can try it immediately, and each run spends credits according to its tier — a large run costs more than a small one, and estimate_simulation_size_and_cost will tell you which tier a graph falls into before you run it. A Kromatic membership does not include Neumann access or a discount; the two are priced separately.

Buying additional credits is not enabled yet. Card payment is still being switched on, so the buy_credits tool and the checkout endpoints currently return a “billing unavailable” error. If you run out of starter credits, or you know up front that you need more, reach us through the contact form and we will sort it out directly.

The price per credit is published by the service itself at https://neumann.kromatic.com/billing/pricing, so it is always the live number rather than a figure copied onto this page.