Buildkite

Developer ToolsPublisher: Buildkite

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

Block risky tools, such as cancel_build.
Mask sensitive data in tool results, such as emails in current_user responses.
Keep credentials at the Connector, so users and agents never see Buildkite 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 Buildkite MCP server to your Resources

UI
Terraform
Pulumi
API

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

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

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

Under OAuth app, keep Formal’s App.

Formal’s App (default)

Formal has a registered OAuth app with Buildkite, so you register nothing. Users see Formal on Buildkite’s consent screen.

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.buildkite.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 buildkite-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.buildkite.com",
    "post_tls": true
  },
  "outputs": {
    "forward_to_connector": true
  }
}

resource "formal_network_rule" "buildkite_mcp" {
  name        = "buildkite-mcp"
  description = "Forward Buildkite 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.buildkite.com",
        "post_tls": true
      },
      "outputs": {
        "forward_to_connector": true
      }
    }
  EOT
}

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

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

4. Create policies

Tools

The Admin Catalog lists these tools for Buildkite:

Tool	Description
`current_user`	Get the user who owns the connection.
`list_pipelines`	List pipelines in an organization.
`create_build`	Start a build on a pipeline.
`cancel_build`	Cancel a build.
`retry_job`	Retry a failed job.
`unblock_job`	Unblock a blocked job.
`list_clusters`	List clusters in an organization.
`list_cluster_queues`	List a cluster’s queues.
`list_agents`	List agents and their connection state.

Policies examples

Block a tool
Mask a tool's output

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

package formal.v2

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

write_tools := {
  "create_build",
  "cancel_build",
  "retry_job",
  "unblock_job",
}

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

This policy replaces email addresses in results returned by current_user.

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 Buildkite results",
} if {
  input.resource.name == "buildkite"
  input.mcp.tool_name in {"current_user"}
  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:buildkite. Each Buildkite 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 Buildkite rejected your credentials

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

2. Setup Authentication

Formal’s App (default)

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 Buildkite MCP server to your Resources

​2. Setup Authentication

​Formal’s App (default)

​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 Buildkite MCP server to your Resources

2. Setup Authentication

Formal’s App (default)

3. Route Endpoint traffic

4. Create policies

Tools

Policies examples

5. Check the logs

Troubleshooting

Next Steps