MCP deployment

Model Context Protocol (MCP) lets an assistant discover and call tools. A Sim workflow MCP server groups deployed workflows into tools an external client can invoke.

You need workspace Admin access to create or change workflow MCP servers and add or remove workflow tools. Organization permission groups can also restrict MCP deployment. Read access lets members view servers.

Create an MCP server

Open Settings → MCP Servers and click Add.
Enter a name and optional description.
Choose API Key or Public access.
Optionally select already-deployed workflows to add immediately.
Click Add Server, then open Details and copy its URL.

Private clients send X-API-Key when connecting. For public servers, omit that header.

A public server exposes its configured workflow tools without authentication. Review the actions and outputs of every tool on the server before enabling public access.

Add a workflow as a tool

Deploy the workflow before adding it to a server:

Open the workflow's Deploy → MCP tab.
Enter the tool name and description.
Review the parameters derived from the deployed Start inputs.
Select the MCP servers that should expose the tool.
Click Save Tool.
Connect a client and confirm that it lists and can call the tool. Check the run in Logs.

Tools execute the workflow's active deployment, like ordinary API calls. Deploy an update after changing workflow logic or inputs.

Tool configuration

Tool name

Use lowercase letters, numbers, and underscores, such as search_documents. Choose a name that distinguishes the action from other tools on the server.

Description

Describe what the workflow does and when it should be called. A blank description falls back to the workflow's description when available.

Parameters

The workflow's deployed input fields become tool parameters. Their descriptions default to the descriptions on Start's Inputs. Set a per-tool override only when that tool needs different wording; it does not edit Start.

Redeploy to make changes to Start fields and default descriptions available to the tool. Preserve meaningful descriptions so the client knows what values to supply.

Connect an MCP client

Open your server's Details, copy its URL, and choose a client under MCP Client. The UI offers client presets, but check the current client documentation when its configuration differs from a generated example.

The examples below connect directly over HTTP. Replace YOUR_SERVER_URL; private servers also require a valid Sim API key. For public servers, remove the authentication header settings.

Cursor

In .cursor/mcp.json, use Cursor's environment interpolation syntax:

{
  "mcpServers": {
    "my-sim-workflows": {
      "url": "YOUR_SERVER_URL",
      "headers": { "X-API-Key": "${env:SIM_API_KEY}" }
    }
  }
}

Make SIM_API_KEY available to the Cursor process. Cursor also has a one-click install link in Sim's server details. See Cursor's MCP configuration.

Codex

In ~/.codex/config.toml:

[mcp_servers."my-sim-workflows"]
url = "YOUR_SERVER_URL"
env_http_headers = { "X-API-Key" = "SIM_API_KEY" }

Set SIM_API_KEY in the environment before starting Codex. env_http_headers maps a header name to an environment-variable name; it does not contain the key itself. See official OpenAI MCP documentation.

Claude Code

claude mcp add --transport http my-sim-workflows 'YOUR_SERVER_URL' \
  --header "X-API-Key: $SIM_API_KEY"

The shell expands the variable in this command. Follow Claude Code's MCP instructions for configuration scope and authentication.

Claude Desktop

Add a remote custom connector with the server URL. For a private server, add X-API-Key and its value under Request headers. For a public server, use the no-sign-in configuration without a key.

Remote connectors reach the server from Anthropic's infrastructure, even when used in Claude Desktop. The server must be reachable from that service; a URL reachable only on your computer is insufficient. Team/Enterprise connector administration also has its own Claude-side permissions. See Claude's current custom-connector setup.

VS Code

Use direct HTTP in .vscode/mcp.json. An input prompt keeps the key out of the checked-in configuration:

{
  "inputs": [
    {
      "type": "promptString",
      "id": "sim-api-key",
      "description": "Sim API key",
      "password": true
    }
  ],
  "servers": {
    "my-sim-workflows": {
      "type": "http",
      "url": "YOUR_SERVER_URL",
      "headers": { "X-API-Key": "${input:sim-api-key}" }
    }
  }
}

For a public server, remove headers and the unused input. See VS Code's MCP configuration reference.

Action	Required workspace role
View workflow MCP servers	Read, Write, or Admin
Create, update, or delete workflow MCP servers	Admin
Add or remove workflow tools	Admin

These management operations do not accept workspace API keys. Invoking a private server is a separate authenticated operation with its own key/OAuth access and scope requirements.