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Claude for Excel and ModelRisk MCP — the honest status

TL;DR: Claude for Excel cannot currently reach this server. Use Claude Desktop or Claude Code (local stdio) instead — modelrisk-mcp install wires both. This page replaces earlier instructions that described a Settings → Connectors flow inside the add-in; those instructions were wrong for shipping builds and are withdrawn (verified 2026-07 against a current build, and independently confirmed by a field report).

Why it can't work today

Claude for Excel is an Office.js add-in running in a browser WebView. Its connector model has three properties that together rule out a local, Excel-driving MCP server:

  1. No local Connectors panel. The add-in's settings contain no "Add MCP server" entry. It resolves connectors from your claude.ai account connector list.
  2. claude.ai custom connectors are remote. The "Add custom connector" dialog takes a remote MCP server URL plus OAuth credentials, and those connectors are fetched by Anthropic's infrastructure, not by your device. A loopback URL (http://127.0.0.1:8000/mcp) is unreachable by construction — no configuration makes it work. The OAuth fields also don't match this server's bearer-token auth.
  3. Local stdio servers never appear in the "Connectors" panel on claude.ai or Claude Desktop. That's normal: the Connectors panel lists account-level remote connectors; local stdio servers are a separate, Desktop-only mechanism. Not seeing modelrisk there does not mean the install failed.

The server side is fine — the HTTP transport handshakes correctly and enforces its bearer token (401 without it). The limitation is entirely in how the client resolves connectors.

Do not tunnel around this

The only technically-possible route to Claude for Excel today would be exposing the server through a public tunnel with OAuth in front. We do not recommend or support this. This server can write formulas into your workbooks, run simulations, and save files to disk. A publicly reachable instance guarded by a single bearer token is a materially different security posture from the loopback bind these docs are written around. If your organisation genuinely needs an in-Excel path, contact Vose — that is a product decision (a hosted connector with real auth), not a configuration setting.

What to use instead

Client Transport Status
Claude Desktop local stdio ✅ Supported, tested — modelrisk-mcp install
Claude Code local stdio ✅ Supported, tested — modelrisk-mcp install (0.3.11+; earlier versions wrote the wrong config file)
Cursor / Zed / other local MCP clients local stdio ✅ Works; configure manually
An MCP client running on your own machine/LAN --transport=streamable-http + bearer token ✅ Works — keep the default loopback bind
Claude for Excel — ❌ Not reachable by current builds

Everything this server does — building models, running simulations, reading results, charts, reports — works identically from Claude Desktop and Claude Code against the same Excel session you have open. Excel and ModelRisk are driven either way; only the chat window lives elsewhere.

HTTP transport (for clients that do run on your machine)

$env:MODELRISK_MCP_TOKEN = [Guid]::NewGuid().ToString("N") * 2
modelrisk-mcp --transport=streamable-http --host=127.0.0.1 --port=8000 --token=$env:MODELRISK_MCP_TOKEN
  • POST /mcp with Authorization: Bearer <token> → MCP initialize handshake.
  • No token → 401.
  • Keep --host=127.0.0.1 unless you fully understand the exposure of 0.0.0.0 on your network.
  • Add --read-only for a first session against a model you care about (0.3.11+): reading and analysis work; writes, simulations and saves are refused with a clear error.

If Anthropic's connector model changes

If a future Claude for Excel build adds local MCP support or a device-fetched connector mode, this page will be updated and the client re-tested before instructions are published. Watch the CHANGELOG.