Railway

Developer ToolsPublisher: Railway

Route Railway MCP traffic through Formal to control and log what AI agents do in Railway:

Block risky tools, such as update_service.
Mask sensitive data in tool results, such as secrets and API keys in list_deployments responses.
Keep credentials at the Connector, so users and agents never see Railway tokens.
Log every tool call with the user, the MCP client and its parameters.

0. Prepare your Connector

The Connector needs an MCP listener and a hostname with wildcard DNS and TLS. Set them up once by following Deploy the Connector. Every MCP server reuses them.

1. Add Railway MCP server to your Resources

UI
Terraform
Pulumi
API

Open the Admin Catalog and click Add MCP.
Select the Railway template.
Enter a DNS-label Name, such as railway.
Choose the Space containing your Connector, such as default.
Configure upstream authentication as described below, then save.

If no Connector is in the selected Space, the Configuration tab shows MCP clients can’t connect directly yet. The reason reads: No Connector is in this server's Space.

Set space_id to the ID of the Space containing your Connector.

resource "formal_resource" "railway" {
  name                    = "railway"
  technology              = "mcp"
  hostname                = "mcp.railway.com"
  space_id                = "<SPACE_ID>"
  native_users_v3_enabled = true
  port                    = 443
  tags = {
    "mcp-endpoint" = "/mcp"
  }
}

resource "formal_resource_oauth_settings" "railway" {
  resource_id = formal_resource.railway.id
}

Set spaceId to the ID of the Space containing your Connector.

import * as formal from "@formalco/pulumi";

const resource = new formal.Resource("mcp", {
  name: "railway",
  technology: "mcp",
  hostname: "mcp.railway.com",
  port: 443,
  spaceId: "<SPACE_ID>",
  tags: { "mcp-endpoint": "/mcp" },
  nativeUsersV3Enabled: true,
});

new formal.ResourceOauthSettings("mcpOAuth", {
  resourceId: resource.id,
});

Create a Resource with the MCP endpoint and its Space ID.

export FORMAL_API_KEY="<YOUR_API_KEY>"
RESOURCE_RESPONSE=$(curl --fail --silent --show-error \
  --request POST \
  https://api.formal.ai/core.v1.ResourceService/CreateResource \
  --header "x-api-key: ${FORMAL_API_KEY}" \
  --header "Content-Type: application/json" \
  --data-binary @- <<JSON
  {
    "name": "railway",
    "hostname": "mcp.railway.com",
    "port": 443,
    "technology": "mcp",
    "spaceId": "<SPACE_ID>",
    "tags": [
      {
        "key": "mcp-endpoint",
        "value": "/mcp"
      }
    ]
  }
JSON
)
RESOURCE_ID=$(printf '%s' "${RESOURCE_RESPONSE}" | jq -r '.resource.id')
curl --fail --silent --show-error \
  --request POST \
  https://api.formal.ai/core.v1.ResourceService/CreateResourceOAuthSettings \
  --header "x-api-key: ${FORMAL_API_KEY}" \
  --header "Content-Type: application/json" \
  --data-binary @- <<JSON
  {
    "resourceId": "${RESOURCE_ID}"
  }
JSON

2. Setup Authentication

Linked Accounts (Recommended)
Shared Credentials
Pass Through

Each user links their own Railway account once in the Employee Catalog, and the Connector sends that user’s token to Railway.

Linked Accounts selected under How does Formal authenticate to this resource?

Under OAuth app, choose one of the two options.

1. Formal’s App (default)

Railway supports Client ID Metadata Documents, so you register nothing. Users see Formal on Railway’s consent screen.

2. Your OAuth App

Users see your app’s name on Railway’s consent screen.

Set up your own Railway OAuth app

See Railway OAuth documentation and register an app.

Open your Railway workspace settings, select Developer, and click New OAuth App.

Choose the application type

Enter a name and select Web (Confidential) for a server-side application with a secret.

Configure the callback

Add Formal’s Redirect URI to Redirect URIs, matching the scheme, host, port, and path exactly.

Request MCP access

Request workspace:member in the authorization request’s scope parameter.

Save the credentials

Create the app and copy its Client ID and Client secret; the secret appears only once. You can skip the client secret. Formal then authenticates with PKCE alone.

Enter the app in Formal

UI
Terraform
Pulumi
API

Back in the Admin Catalog, enter the Client ID and Client secret, then save. Users then link their accounts on the Railway server’s page in the Employee Catalog.

Your OAuth App selected in the Admin Catalog, with the Redirect URI, Client ID and Client secret fields

Use these OAuth settings instead of the ones from step 1.

variable "railway_oauth_client_secret" {
  type      = string
  sensitive = true
}

resource "formal_resource_oauth_settings" "railway" {
  resource_id              = formal_resource.railway.id
  upstream_oauth_mode      = "pre_registered"
  client_id                = "<YOUR_CLIENT_ID>"
  client_secret_wo         = var.railway_oauth_client_secret
  client_secret_wo_version = 1
}

Use these OAuth settings instead of the ones from step 1. Store the secret with pulumi config set --secret railwayOauthClientSecret.

import * as pulumi from "@pulumi/pulumi";

const config = new pulumi.Config();

new formal.ResourceOauthSettings("mcpOAuth", {
  resourceId: resource.id,
  upstreamOauthMode: "pre_registered",
  clientId: "<YOUR_CLIENT_ID>",
  clientSecret: config.requireSecret("railwayOauthClientSecret"),
});

Use this call instead of the CreateResourceOAuthSettings call from step 1. The OAuth app is fixed at creation.

curl --fail --silent --show-error \
  --request POST \
  https://api.formal.ai/core.v1.ResourceService/CreateResourceOAuthSettings \
  --header "x-api-key: ${FORMAL_API_KEY}" \
  --header "Content-Type: application/json" \
  --data-binary @- <<JSON
  {
    "resourceId": "${RESOURCE_ID}",
    "upstreamOauthMode": "pre_registered",
    "clientId": "<YOUR_CLIENT_ID>",
    "clientSecret": "<YOUR_CLIENT_SECRET>"
  }
JSON

Switching between Formal’s App and your OAuth app unlinks every account. Users must link again.

3. Route Endpoint traffic

Auth is managed at the Connector level when you use Linked Accounts or Shared Credentials, so the Endpoint needs to forward the MCP traffic to it. Laptops and VMs with the Formal Endpoint keep using https://mcp.railway.com/mcp, and a network rule sends that traffic to the Connector.

UI
Terraform
Pulumi
API

Go to Network Rules and create a rule named railway-mcp.
Paste this expression, set the rule to Active, then save:

{
  "condition": {
    "pre_tcp": process.is_agent,
    // Every MCP server added to Formal: process.is_agent && resource.technology == "mcp"
    "pre_tls": process.is_agent && hostname == "mcp.railway.com",
    "post_tls": true
  },
  "outputs": {
    "forward_to_connector": true
  }
}

resource "formal_network_rule" "railway_mcp" {
  name        = "railway-mcp"
  description = "Forward Railway MCP traffic from agents to the Connector"
  status      = "active"

  # Every MCP server added to Formal: set pre_tls to process.is_agent && resource.technology == "mcp"
  cel_expression = <<-EOT
    {
      "condition": {
        "pre_tcp": process.is_agent,
        "pre_tls": process.is_agent && hostname == "mcp.railway.com",
        "post_tls": true
      },
      "outputs": {
        "forward_to_connector": true
      }
    }
  EOT
}

import * as formal from "@formalco/pulumi";

new formal.NetworkRule("railwayMcp", {
  name: "railway-mcp",
  description: "Forward Railway MCP traffic from agents to the Connector",
  status: "active",
  // Every MCP server added to Formal: set pre_tls to process.is_agent && resource.technology == "mcp"
  celExpression: `
    {
      "condition": {
        "pre_tcp": process.is_agent,
        "pre_tls": process.is_agent && hostname == "mcp.railway.com",
        "post_tls": true
      },
      "outputs": {
        "forward_to_connector": true
      }
    }
  `,
});

export FORMAL_API_KEY="<YOUR_API_KEY>"
# Every MCP server added to Formal: set pre_tls to process.is_agent && resource.technology == "mcp"
CEL_EXPRESSION=$(cat <<'CEL'
{
  "condition": {
    "pre_tcp": process.is_agent,
    "pre_tls": process.is_agent && hostname == "mcp.railway.com",
    "post_tls": true
  },
  "outputs": {
    "forward_to_connector": true
  }
}
CEL
)
jq -n --arg cel "${CEL_EXPRESSION}" '{
  name: "railway-mcp",
  description: "Forward Railway MCP traffic from agents to the Connector",
  status: "active",
  celExpression: $cel
}' | curl --fail --silent --show-error \
  --request POST \
  https://api.formal.ai/core.v1.DesktopService/CreateDesktopRoutingRule \
  --header "x-api-key: ${FORMAL_API_KEY}" \
  --header "Content-Type: application/json" \
  --data-binary @-

The rule matches known agents only. See Identity headers.Cloud agents such as Claude, ChatGPT and Cursor Cloud Agents don’t run the Endpoint. Point them at this server’s Connector address, https://railway.<connector-hostname>/mcp. Find it in the Admin Catalog: open Railway, then copy Connector address on the Configuration tab.

4. Create policies

Tools

The Admin Catalog lists these tools for Railway:

Tool	Description
`list_projects`	List your projects.
`create_project`	Create a project.
`list_services`	List a project’s services.
`create_service`	Create a service.
`get_service_config`	Get a service’s configuration.
`update_service`	Update a service.
`create_environment`	Create an environment.
`list_deployments`	List a service’s deployments.
`list_variables`	List a service’s variables.
`set_variables`	Set a service’s variables.

Policies examples

Block a tool
Mask a tool's output

This policy blocks the tools that change data, so agents can only read Railway.

package formal.v2

import future.keywords.if
import future.keywords.in

write_tools := {
  "create_project",
  "create_service",
  "update_service",
  "create_environment",
  "set_variables",
}

request := {
  "action": "block",
  "type": "block_with_custom_message",
  "message": "Writing to Railway is not allowed.",
} if {
  input.resource.name == "railway"
  input.mcp.method == "tools/call"
  input.mcp.tool_name in write_tools
}

This policy replaces email addresses in results returned by list_deployments and list_variables.

package formal.v2

import future.keywords.if
import future.keywords.in

email_pattern := `[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,}`

response := {
  "action": "rewrite",
  "body": regex.replace(input.http.body, email_pattern, "[REDACTED-EMAIL]"),
  "reason": "Mask emails in Railway results",
} if {
  input.resource.name == "railway"
  input.mcp.tool_name in {"list_deployments", "list_variables"}
  regex.match(email_pattern, input.http.body)
}

See MCP resources for the input.mcp fields and Rewrite Action for body rewrites.

5. Check the logs

Open Logs and search for resource.name:railway. Each Railway tool call is one request log with the user, the MCP client and the tool. Open a log to see its tool parameters and the policies it triggered. A blocked write shows the block policy and its message. A masked search shows the rewrite policy.See Logs for search syntax and filters.

Troubleshooting

The agent says Railway rejected your credentials

The agent relays: railway rejected your credentials. Link or re-link your railway account in Formal…Cause: Railway no longer accepts the linked token, for example after the user revoked access in Railway.Fix: Link Railway again from the Employee Catalog.

Laptop traffic doesn't appear in Logs

Cause: The Endpoint isn’t running, or the network rule doesn’t match the client.Fix: Check the Endpoint is connected. The rule above only matches known agents. Other clients, such as a browser, reach Railway directly unless the rule also matches them. See Network rules.

MCP clients can't connect directly yet

Cause: The Configuration tab lists the reason, most often No Connector is in this server's Space.Fix: Edit the server and choose the Space containing its Connector.

Getting Started

Example Use Cases

AI Governance

Configuring Formal

Integrations

Configuration

0. Prepare your Connector

1. Add Railway MCP server to your Resources

2. Setup Authentication

1. Formal’s App (default)

2. Your OAuth App

3. Route Endpoint traffic

4. Create policies

Tools

Policies examples

5. Check the logs

Troubleshooting

Next Steps

MCP Gateway

All MCP servers

​0. Prepare your Connector

​1. Add Railway MCP server to your Resources

​2. Setup Authentication

​1. Formal’s App (default)

​2. Your OAuth App

​3. Route Endpoint traffic

​4. Create policies

​Tools

​Policies examples

​5. Check the logs

​Troubleshooting

​Next Steps

MCP Gateway

All MCP servers

0. Prepare your Connector

1. Add Railway MCP server to your Resources

2. Setup Authentication

1. Formal’s App (default)

2. Your OAuth App

3. Route Endpoint traffic

4. Create policies

Tools

Policies examples

5. Check the logs

Troubleshooting

Next Steps