Fix MCP error responses and share endpoint redaction

Author: cursoragent

Sources/agentd/AgentdMCP.swift

@@ -79,7 +79,7 @@ struct SystemAgentdMCPRuntime: AgentdMCPRuntime {
       deviceId: config.deviceId,
       organizationId: config.organizationId,
       mode: config.localOnly ? "local-only" : "managed",
-      endpoint: Self.redactEndpoint(config.endpoint),
+      endpoint: EndpointRedaction.redact(config.endpoint),
       permissions: AgentdMCPPermissionStatus(
         accessibilityTrusted: permissions.accessibilityTrusted,
         screenCaptureTrusted: permissions.screenCaptureTrusted,
@@ -112,13 +112,6 @@ struct SystemAgentdMCPRuntime: AgentdMCPRuntime {
     )
   }
 
-  private static func redactEndpoint(_ endpoint: URL) -> String {
-    var components = URLComponents(url: endpoint, resolvingAgainstBaseURL: false)
-    components?.query = nil
-    components?.user = nil
-    components?.password = nil
-    return components?.url?.absoluteString ?? "[redacted]"
-  }
 }
 
 struct AgentdMCPServer {
@@ -128,8 +121,24 @@ struct AgentdMCPServer {
     self.runtime = runtime
   }
 
-  func handle(_ data: Data) async throws -> Data {
-    let request = try AgentdMCPRequest(data: data)
+  func handle(_ data: Data) async -> Data {
+    do {
+      let request = try AgentdMCPRequest(data: data)
+      do {
+        return try await handleRequest(request)
+      } catch {
+        let mcpError = Self.jsonRPCError(for: error)
+        return safeErrorResponse(id: request.id, code: mcpError.code, message: mcpError.message)
+      }
+    } catch let error as AgentdMCPError {
+      let mcpError = Self.jsonRPCError(for: error)
+      return safeErrorResponse(id: nil, code: mcpError.code, message: mcpError.message)
+    } catch {
+      return safeErrorResponse(id: nil, code: -32700, message: "parse error")
+    }
+  }
+
+  private func handleRequest(_ request: AgentdMCPRequest) async throws -> Data {
     switch request.method {
     case "initialize":
       return try response(
@@ -230,6 +239,12 @@ struct AgentdMCPServer {
     ])
   }
 
+  private func safeErrorResponse(id: Any?, code: Int, message: String) -> Data {
+    (try? errorResponse(id: id, code: code, message: message))
+      ?? (Data(#"{"error":{"code":-32603,"message":"internal error"},"id":null,"jsonrpc":"2.0"}"#.utf8)
+        + Data([0x0A]))
+  }
+
   private static func toolCatalog() -> [[String: Any]] {
     [
       [
@@ -285,6 +300,17 @@ struct AgentdMCPServer {
     try JSONSerialization.data(withJSONObject: object, options: [.prettyPrinted, .sortedKeys])
       + Data([0x0A])
   }
+
+  private static func jsonRPCError(for error: Error) -> (code: Int, message: String) {
+    switch error {
+    case let error as AgentdMCPError:
+      return (error.code, error.localizedDescription)
+    case let error as DiagnosticCLIError:
+      return (-32602, error.localizedDescription)
+    default:
+      return (-32603, error.localizedDescription)
+    }
+  }
 }
 
 struct AgentdMCPRequest {
@@ -308,6 +334,13 @@ struct AgentdMCPRequest {
 enum AgentdMCPError: Error, LocalizedError {
   case invalidRequest
 
+  var code: Int {
+    switch self {
+    case .invalidRequest:
+      return -32600
+    }
+  }
+
   var errorDescription: String? {
     switch self {
     case .invalidRequest:
@@ -321,13 +354,9 @@ enum AgentdMCPStdio {
     while let line = readLine(strippingNewline: true) {
       let trimmed = line.trimmingCharacters(in: .whitespacesAndNewlines)
       guard !trimmed.isEmpty else { continue }
-      do {
-        let response = try await server.handle(Data(trimmed.utf8))
-        if !response.isEmpty {
-          FileHandle.standardOutput.write(response)
-        }
-      } catch {
-        FileHandle.standardError.write(Data("agentd mcp: \(error.localizedDescription)\n".utf8))
+      let response = await server.handle(Data(trimmed.utf8))
+      if !response.isEmpty {
+        FileHandle.standardOutput.write(response)
       }
     }
     return 0

Sources/agentd/Diagnostics.swift

@@ -34,7 +34,7 @@ enum DiagnosticsReport {
     lines.append("- Screen capture preflight: \(snapshot.permissions.screenCaptureTrusted)")
     lines.append("- Mode: \(snapshot.config.localOnly ? "local-only" : "managed")")
     lines.append("- Secret Broker: \(snapshot.config.secretBroker == nil ? "disabled" : "enabled")")
-    lines.append("- Endpoint: \(redactEndpoint(snapshot.config.endpoint))")
+    lines.append("- Endpoint: \(EndpointRedaction.redact(snapshot.config.endpoint))")
     lines.append("- Policy version: \(snapshot.policyVersion ?? "none")")
     lines.append("- Policy source: \(redact(snapshot.policySource ?? "none"))")
     lines.append("- Last control error: \(redact(snapshot.controlError ?? "none"))")
@@ -185,14 +185,6 @@ enum DiagnosticsReport {
     return redact(value)
   }
 
-  private static func redactEndpoint(_ endpoint: URL) -> String {
-    var components = URLComponents(url: endpoint, resolvingAgainstBaseURL: false)
-    components?.query = nil
-    components?.user = nil
-    components?.password = nil
-    return components?.url?.absoluteString ?? "[redacted]"
-  }
-
   private static func iso(_ date: Date) -> String {
     ISO8601DateFormatter().string(from: date)
   }

Sources/agentd/EndpointRedaction.swift

@@ -0,0 +1,13 @@
+// SPDX-License-Identifier: BUSL-1.1
+
+import Foundation
+
+enum EndpointRedaction {
+  static func redact(_ endpoint: URL) -> String {
+    var components = URLComponents(url: endpoint, resolvingAgainstBaseURL: false)
+    components?.query = nil
+    components?.user = nil
+    components?.password = nil
+    return components?.url?.absoluteString ?? "[redacted]"
+  }
+}

Tests/agentdTests/AgentdMCPTestSupport.swift

@@ -33,15 +33,24 @@ final class AgentdMCPRuntimeStub: AgentdMCPRuntime {
     instructionsPath: "/tmp/instructions.md",
     resourcePaths: ["/tmp/resources/activity.md"]
   )
+  var deviceSnapshotError: Error?
+  var activityError: Error?
+  var diagnosticsError: Error?
   private(set) var requestedActivity: ActivityOptions?
   private(set) var requestedDiagnostics: ActivityOptions?
   private(set) var requestedDiagnosticsOutDir: URL?
 
   func deviceSnapshot() async throws -> AgentdMCPDeviceSnapshot {
+    if let deviceSnapshotError {
+      throw deviceSnapshotError
+    }
     deviceSnapshot
   }
 
   func activityRecent(options: ActivityOptions) async throws -> ActivitySummary {
+    if let activityError {
+      throw activityError
+    }
     requestedActivity = options
     return activitySummary.replacing(
       batchDirectory: options.batchDirectory.path,
@@ -52,6 +61,9 @@ final class AgentdMCPRuntimeStub: AgentdMCPRuntime {
   func collectDiagnostics(options: ActivityOptions, outputDirectory: URL) async throws
     -> AgentdMCPDiagnosticsResult
   {
+    if let diagnosticsError {
+      throw diagnosticsError
+    }
     requestedDiagnostics = options
     requestedDiagnosticsOutDir = outputDirectory
     return diagnosticsResult
@@ -74,6 +86,12 @@ func mcpText(_ data: Data) throws -> String {
   return try XCTUnwrap(content.first?["text"] as? String)
 }
 
+struct AgentdMCPStubError: LocalizedError {
+  let message: String
+
+  var errorDescription: String? { message }
+}
+
 extension ActivitySummaryTests {
   static func summary(
     batchDirectory: URL,

Tests/agentdTests/DiagnosticCLITests.swift

@@ -22,8 +22,8 @@ final class DiagnosticCLITests: XCTestCase {
     let runtime = AgentdMCPRuntimeStub()
     let server = AgentdMCPServer(runtime: runtime)
 
-    let initialize = try await server.handle(
-      jsonData(
+    let initialize = await server.handle(
+      try jsonData(
         [
           "jsonrpc": "2.0",
           "id": 1,
@@ -41,8 +41,8 @@ final class DiagnosticCLITests: XCTestCase {
     let initializeResult = try XCTUnwrap(initializeRoot["result"] as? [String: Any])
     XCTAssertEqual(initializeResult["protocolVersion"] as? String, "2025-06-18")
 
-    let tools = try await server.handle(
-      jsonData(["jsonrpc": "2.0", "id": "tools", "method": "tools/list"]))
+    let tools = await server.handle(
+      try jsonData(["jsonrpc": "2.0", "id": "tools", "method": "tools/list"]))
     let toolsRoot = try jsonObject(tools)
     let toolsResult = try XCTUnwrap(toolsRoot["result"] as? [String: Any])
     let toolList = try XCTUnwrap(toolsResult["tools"] as? [[String: Any]])
@@ -85,8 +85,8 @@ final class DiagnosticCLITests: XCTestCase {
     )
     let server = AgentdMCPServer(runtime: runtime)
 
-    let response = try await server.handle(
-      jsonData([
+    let response = await server.handle(
+      try jsonData([
         "jsonrpc": "2.0",
         "id": "activity",
         "method": "tools/call",
@@ -123,8 +123,8 @@ final class DiagnosticCLITests: XCTestCase {
     )
     let server = AgentdMCPServer(runtime: runtime)
 
-    let response = try await server.handle(
-      jsonData([
+    let response = await server.handle(
+      try jsonData([
         "jsonrpc": "2.0",
         "id": "diag",
         "method": "tools/call",
@@ -173,8 +173,8 @@ final class DiagnosticCLITests: XCTestCase {
     )
     let server = AgentdMCPServer(runtime: runtime)
 
-    let response = try await server.handle(
-      jsonData([
+    let response = await server.handle(
+      try jsonData([
         "jsonrpc": "2.0",
         "id": "snapshot",
         "method": "tools/call",
@@ -193,6 +193,65 @@ final class DiagnosticCLITests: XCTestCase {
     XCTAssertEqual(privacy["deniedPathPrefixCount"] as? Int, 2)
   }
 
+  func testMcpInvalidRequestsReturnJsonRpcErrorResponses() async throws {
+    let server = AgentdMCPServer(runtime: AgentdMCPRuntimeStub())
+
+    let missingMethod = await server.handle(
+      try jsonData(["jsonrpc": "2.0", "id": 1, "params": [:]])
+    )
+    let invalidRoot = try jsonObject(missingMethod)
+    let invalidError = try XCTUnwrap(invalidRoot["error"] as? [String: Any])
+    XCTAssertTrue(invalidRoot["id"] is NSNull)
+    XCTAssertEqual(invalidError["code"] as? Int, -32600)
+    XCTAssertEqual(invalidError["message"] as? String, "invalid MCP JSON-RPC request")
+
+    let malformed = await server.handle(Data("{".utf8))
+    let malformedRoot = try jsonObject(malformed)
+    let malformedError = try XCTUnwrap(malformedRoot["error"] as? [String: Any])
+    XCTAssertTrue(malformedRoot["id"] is NSNull)
+    XCTAssertEqual(malformedError["code"] as? Int, -32700)
+    XCTAssertEqual(malformedError["message"] as? String, "parse error")
+  }
+
+  func testMcpThrownToolErrorsReturnJsonRpcErrorResponses() async throws {
+    let runtime = AgentdMCPRuntimeStub()
+    runtime.deviceSnapshotError = AgentdMCPStubError(message: "snapshot failed")
+    runtime.activityError = DiagnosticCLIError.usage("--window requires one of 10m, 6h, or 24h")
+    let server = AgentdMCPServer(runtime: runtime)
+
+    let snapshotResponse = await server.handle(
+      try jsonData([
+        "jsonrpc": "2.0",
+        "id": "snapshot-error",
+        "method": "tools/call",
+        "params": [
+          "name": "agentd_device_snapshot",
+          "arguments": [:],
+        ],
+      ]))
+    let snapshotRoot = try jsonObject(snapshotResponse)
+    let snapshotError = try XCTUnwrap(snapshotRoot["error"] as? [String: Any])
+    XCTAssertEqual(snapshotRoot["id"] as? String, "snapshot-error")
+    XCTAssertEqual(snapshotError["code"] as? Int, -32603)
+    XCTAssertEqual(snapshotError["message"] as? String, "snapshot failed")
+
+    let activityResponse = await server.handle(
+      try jsonData([
+        "jsonrpc": "2.0",
+        "id": "activity-error",
+        "method": "tools/call",
+        "params": [
+          "name": "agentd_activity_recent",
+          "arguments": ["window": "6h"],
+        ],
+      ]))
+    let activityRoot = try jsonObject(activityResponse)
+    let activityError = try XCTUnwrap(activityRoot["error"] as? [String: Any])
+    XCTAssertEqual(activityRoot["id"] as? String, "activity-error")
+    XCTAssertEqual(activityError["code"] as? Int, -32602)
+    XCTAssertEqual(activityError["message"] as? String, "--window requires one of 10m, 6h, or 24h")
+  }
+
   func testCaptureOnceParserAcceptsSafeFlags() throws {
     let command = try DiagnosticCommand.parse([
       "capture-once", "--display-id", "42", "--no-ocr", "--out", "/tmp/agentd.json",