Grant access to MCP tools

When you register MCP servers with Aperture, users can access tools, resources, and templates through the Aperture proxy. Like model access, MCP access is deny-by-default. You need to configure grants that specify which MCP items each user or group can use.

This guide assumes you have already configured model access grants. MCP grants use the same structure, with additional capability fields for MCP items.

Prerequisites

Before you begin, ensure you have the following:

• An Aperture instance with at least one configured provider and at least one registered MCP server.
• Admin access to the Aperture dashboard.
• Users who already have a role grant and network access to the Aperture device. If not, complete Grant access to models first.

Configure MCP access grants

Add MCP capability fields to your grants to control which MCP items users can access. You can grant access to three types of MCP items: tools, resources, and templates.

Open the Settings page of the Aperture dashboard and add MCP fields to the tailscale.com/cap/aperture capability array.

The following example grants users in group:ai-users access to all tools from the local MCP server and all resources from any server:

{
  "grants": [
    {
      "src": ["group:ai-users"],
      "app": {
        "tailscale.com/cap/aperture": [
          { "role": "user" },
          { "models": "anthropic/**" },
          { "mcp_tools": "local/*" },
          { "mcp_resources": "**" }
        ]
      }
    }
  ]
}

Matching group: sources, like group:ai-users in the example above, requires visible groups enabled for the Aperture device.

MCP capability fields

Each capability entry under tailscale.com/cap/aperture can include these MCP fields:

Patterns use the same glob syntax as model grants: * matches any characters within a single path segment (it does not cross /), and ** matches zero or more segments.

Pattern examples

The following examples show how to use patterns to grant access to specific MCP items:

Next steps

• Grant access to models to manage which LLM models users can access.
• Refer to the grants configuration reference for the full grants syntax.
• Set per-user spending limits to manage costs across models and tools.