Gmail

CommunicationPublisher: Google

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

Block risky tools, such as delete_label.
Mask sensitive data in tool results, such as emails and phone numbers in search_threads responses.
Keep credentials at the Connector, so users and agents never see Gmail 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 Gmail MCP server to your Resources

UI
Terraform
Pulumi
API

Open the Admin Catalog and click Add MCP.
Select the Gmail template.
Enter a DNS-label Name, such as gmail.
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" "gmail" {
  name                    = "gmail"
  technology              = "mcp"
  hostname                = "gmailmcp.googleapis.com"
  space_id                = "<SPACE_ID>"
  native_users_v3_enabled = true
  port                    = 443
  tags = {
    "mcp-endpoint" = "/mcp/v1"
  }
}

resource "formal_resource_oauth_settings" "gmail" {
  resource_id = formal_resource.gmail.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: "gmail",
  technology: "mcp",
  hostname: "gmailmcp.googleapis.com",
  port: 443,
  spaceId: "<SPACE_ID>",
  tags: { "mcp-endpoint": "/mcp/v1" },
  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: ${FORMAL_API_KEY}" \
  --header "Content-Type: application/json" \
  --data-binary @- <<JSON
  {
    "name": "gmail",
    "hostname": "gmailmcp.googleapis.com",
    "port": 443,
    "technology": "mcp",
    "spaceId": "<SPACE_ID>",
    "tags": [
      {
        "key": "mcp-endpoint",
        "value": "/mcp/v1"
      }
    ]
  }
JSON
)
RESOURCE_ID=$(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 Gmail account once in the Employee Catalog, and the Connector sends that user’s token to Gmail.

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

Gmail doesn’t support Formal’s App, so register your own OAuth app.See Gmail OAuth documentation and register an app.

Enable the APIs

In your Google Cloud project, enable the Gmail API and the Gmail MCP API.

Configure the consent screen

Go to Google Auth Platform > Branding and click Get Started. Under Audience, select Internal if available.

Choose scopes

In Data Access, click Add or Remove Scopes. Paste the Gmail scopes under Manually add scopes, then click Update and Save.

Create the client

Go to Clients > Create Client and select Web application. Under Authorized redirect URIs, click + Add URI and paste Formal’s Redirect URI.

Copy the credentials

Select Use this client for an AI-powered agent, click Create, and copy the Client ID and Client secret.

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 Gmail 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 "gmail_oauth_client_secret" {
  type      = string
  sensitive = true
}

resource "formal_resource_oauth_settings" "gmail" {
  resource_id              = formal_resource.gmail.id
  upstream_oauth_mode      = "pre_registered"
  client_id                = "<YOUR_CLIENT_ID>"
  client_secret_wo         = var.gmail_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 gmailOauthClientSecret.

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("gmailOauthClientSecret"),
});

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

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://gmailmcp.googleapis.com/mcp/v1, and a network rule sends that traffic to the Connector.

UI
Terraform
Pulumi
API

Go to Network Rules and create a rule named gmail-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 == "gmailmcp.googleapis.com",
    "post_tls": true
  },
  "outputs": {
    "forward_to_connector": true
  }
}

resource "formal_network_rule" "gmail_mcp" {
  name        = "gmail-mcp"
  description = "Forward Gmail 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 == "gmailmcp.googleapis.com",
        "post_tls": true
      },
      "outputs": {
        "forward_to_connector": true
      }
    }
  EOT
}

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

new formal.NetworkRule("gmailMcp", {
  name: "gmail-mcp",
  description: "Forward Gmail 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 == "gmailmcp.googleapis.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=$(cat <<'CEL'
{
  "condition": {
    "pre_tcp": process.is_agent,
    "pre_tls": process.is_agent && hostname == "gmailmcp.googleapis.com",
    "post_tls": true
  },
  "outputs": {
    "forward_to_connector": true
  }
}
CEL
)
jq -n --arg cel "${CEL_EXPRESSION}" '{
  name: "gmail-mcp",
  description: "Forward Gmail 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://gmail.<connector-hostname>/mcp. Find it in the Admin Catalog: open Gmail, then copy Connector address on the Configuration tab.

4. Create policies

Tools

The Admin Catalog lists these tools for Gmail:

Tool	Description
`search_threads`	Search Gmail conversations.
`get_thread`	Retrieve a complete email thread.
`get_message`	Retrieve an email message.
`send_message`	Send an email message.
`reply`	Reply to an email thread.
`forward`	Forward an email message.
`create_draft`	Create an email draft.
`list_drafts`	List saved drafts.
`trash_message`	Move a message to trash.
`trash_thread`	Move a thread to trash.
`list_labels`	List Gmail labels.
`create_label`	Create a Gmail label.
`delete_label`	Delete a Gmail label.
`label_message`	Apply a label to a message.
`unlabel_message`	Remove a label from a message.
`label_thread`	Apply a label to a thread.
`unlabel_thread`	Remove a label from a thread.
`apply_sensitive_message_label`	Mark a message with the configured sensitive label.
`apply_sensitive_thread_label`	Mark a thread with the configured sensitive label.
`mark_message_spam`	Mark a message as spam.
`unmark_message_spam`	Remove the spam classification from a message.
`mark_thread_spam`	Mark a thread as spam.
`unmark_thread_spam`	Remove the spam classification from a thread.
`list_filters`	List Gmail filters.
`create_filter`	Create a Gmail filter.

Policies examples

Block a tool
Mask a tool's output

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

package formal.v2

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

write_tools := {
  "send_message",
  "reply",
  "forward",
  "create_draft",
  "trash_message",
  "trash_thread",
  "create_label",
  "delete_label",
  "label_message",
  "unlabel_message",
  "label_thread",
  "unlabel_thread",
  "apply_sensitive_message_label",
  "apply_sensitive_thread_label",
  "mark_message_spam",
  "unmark_message_spam",
  "mark_thread_spam",
  "unmark_thread_spam",
  "create_filter",
}

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

This policy replaces email addresses in results returned by search_threads, get_thread, and get_message.

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 Gmail results",
} if {
  input.resource.name == "gmail"
  input.mcp.tool_name in {"search_threads", "get_thread", "get_message"}
  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:gmail. Each Gmail 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 Gmail rejected your credentials

The agent relays: gmail rejected your credentials. Link or re-link your gmail account in Formal…Cause: Gmail no longer accepts the linked token, for example after the user revoked access in Gmail.Fix: Link Gmail 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 Gmail 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 Gmail MCP server to your Resources

2. Setup Authentication

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 Gmail MCP server to your Resources

​2. Setup Authentication

​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 Gmail MCP server to your Resources

2. Setup Authentication

3. Route Endpoint traffic

4. Create policies

Tools

Policies examples

5. Check the logs

Troubleshooting

Next Steps