MCP Resources

MCP resources expose debugger state as read-only, subscribable data views. Unlike tools (which are request-response), resources push updates to subscribed clients whenever the underlying state changes.

Resources vs. Tools

	Tools	Resources
Pattern	Request → Response	Subscribe → Push updates
Use case	Perform actions, query on demand	Monitor state changes
Example	debug_state returns current state	debugger://session pushes on every state change
Best for	One-off queries, actions	Dashboards, watchers, event-driven agents

Available Resources

Resources are only available when a debug session is active. When no session exists, the resource list is empty.

---

debugger://session

Current debug session state, process info, and pause reason.

MIME Type: application/json

Example response:

{
  "processId": 12345,
  "processName": "MyApp",
  "executablePath": "/app/MyApp.dll",
  "runtimeVersion": "10.0.0",
  "state": "Paused",
  "launchMode": "Launch",
  "attachedAt": "2026-02-06T10:30:00Z",
  "pauseReason": "Breakpoint",
  "currentLocation": {
    "file": "/app/Services/UserService.cs",
    "line": 42,
    "column": 8,
    "functionName": "GetUser",
    "moduleName": "MyApp.dll"
  },
  "activeThreadId": 5,
  "commandLineArgs": ["--environment", "Development"],
  "workingDirectory": "/app"
}

Updates when: Session state changes (pause, resume, step, disconnect), current location changes.

---

debugger://breakpoints

All active breakpoints, tracepoints, and exception breakpoints with their status and hit counts.

MIME Type: application/json

Example response:

{
  "breakpoints": [
    {
      "id": "bp-550e8400-e29b-41d4-a716-446655440000",
      "type": "Breakpoint",
      "file": "/app/Services/UserService.cs",
      "line": 42,
      "enabled": true,
      "verified": true,
      "state": "Bound",
      "hitCount": 3,
      "condition": "userId != null",
      "logMessage": null
    },
    {
      "id": "tp-660f9511-f3ac-52e5-b827-557766551111",
      "type": "Tracepoint",
      "file": "/app/Services/OrderService.cs",
      "line": 55,
      "enabled": true,
      "verified": true,
      "state": "Bound",
      "hitCount": 142,
      "logMessage": "Processing order {orderId}",
      "hitCountMultiple": 100,
      "maxNotifications": 0,
      "notificationsSent": 1
    }
  ],
  "exceptionBreakpoints": [
    {
      "id": "ebp-770a0622-a4bd-63f6-c938-668877662222",
      "exceptionType": "System.NullReferenceException",
      "breakOnFirstChance": true,
      "breakOnSecondChance": true,
      "includeSubtypes": true,
      "enabled": true,
      "verified": true,
      "hitCount": 0
    }
  ]
}

Updates when: Breakpoints added, removed, enabled/disabled, or hit count changes.

---

debugger://threads

Thread list with states and current locations.

MIME Type: application/json

Example response:

{
  "threads": [
    {
      "id": 1,
      "name": "Main",
      "state": "Suspended",
      "isCurrent": true,
      "location": {
        "file": "/app/Services/UserService.cs",
        "line": 42,
        "column": 8,
        "functionName": "GetUser",
        "moduleName": "MyApp.dll"
      }
    },
    {
      "id": 5,
      "name": "Worker Thread #1",
      "state": "Suspended",
      "isCurrent": false,
      "location": {
        "file": "/app/Services/BackgroundJob.cs",
        "line": 18,
        "column": 4,
        "functionName": "Execute",
        "moduleName": "MyApp.dll"
      }
    }
  ],
  "stale": false,
  "capturedAt": "2026-02-06T10:30:00Z"
}

Stale data: When the process is running, thread data may be stale (captured at the last pause). The stale field indicates whether the data is current, and capturedAt shows when it was last captured.

Updates when: Process pauses, resumes, or thread states change.

---

debugger://source/{+file}

Source file contents for a given path.

MIME Type: text/plain

URI example: debugger://source//app/Services/UserService.cs

Response: Plain text file contents (no JSON wrapper).

Security: Only source files that belong to loaded modules are accessible. If a file isn't part of the debugged application, the request will fail.

Updates when: This resource is static — it doesn't change during a session.

---

Subscribing to Resources

MCP clients can subscribe to resources to receive push notifications when data changes:

1. Subscribe: Send resources/subscribe with the resource URI
2. Receive updates: The server sends notifications/resources/updated when the resource changes
3. Read new data: Fetch the resource again to get the updated content
4. Unsubscribe: Send resources/unsubscribe when no longer interested

Updates are coalesced — if the same resource changes multiple times in quick succession, you receive a single notification rather than one per change.

Lifecycle

No Session          → resources/list returns []
Session Starts      → resources/list returns all 4 resources
                    → notifications/resources/list_changed sent
Session Active      → resources available, updates sent on changes
Session Disconnects → resources/list returns []
                    → notifications/resources/list_changed sent