3 files changed, 5 insertions, 2 deletions
diff --git a/src/Agent.Core/Tools/InternalToolCatalog.cs b/src/Agent.Core/Tools/InternalToolCatalog.cs
index 1563c16..3ab17b1 100644
--- a/src/Agent.Core/Tools/InternalToolCatalog.cs
+++ b/src/Agent.Core/Tools/InternalToolCatalog.cs
@@ -19,7 +19,8 @@ public static class InternalToolCatalog
             Define("file_read", "Read an approved file.", """{"type":"object","additionalProperties":false,"required":["path","mode"],"properties":{"path":{"type":"string"},"mode":{"type":"string","enum":["whole","range","metadata"]},"start":{"type":"integer","minimum":0},"length":{"type":"integer","minimum":0}}}"""),
             Define("file_edit", "Edit an approved file transactionally.", """{"type":"object","additionalProperties":false,"required":["path","operation"],"properties":{"path":{"type":"string"},"operation":{"type":"string","enum":["overwrite","patch","atomic_replace","delete"]},"content":{"type":["string","null"]},"patch":{"type":["string","null"]},"expected_sha256":{"type":["string","null"]}}}"""),
             Define("process_run", "Run one approved executable with separated arguments.", """{"type":"object","additionalProperties":false,"required":["executable","args","cwd"],"properties":{"executable":{"type":"string"},"args":{"type":"array","items":{"type":"string"}},"cwd":{"type":"string"},"timeout_seconds":{"type":"integer","minimum":1},"stdin":{"type":["string","null"]}}}"""),
-            Define("task_update", "Update the deterministic task graph.", """{"type":"object","additionalProperties":false,"required":["operation"],"properties":{"operation":{"type":"string","enum":["add","add_dependency","set_state","set_estimate"]},"task_id":{"type":["string","null"]},"description":{"type":["string","null"]},"depends_on":{"type":"array","items":{"type":"string"}},"budget_class":{"type":["string","null"],"enum":["1K","2K","4K","8K","16K","32K","64K","128K",null]},"optimistic_tokens":{"type":"integer","minimum":0},"most_likely_tokens":{"type":"integer","minimum":0},"pessimistic_tokens":{"type":"integer","minimum":0},"state":{"type":["string","null"],"enum":["queued","planning","running","completed","failed","cancelled",null]}}}""")
+            Define("task_update", "Update the deterministic task graph.", """{"type":"object","additionalProperties":false,"required":["operation"],"properties":{"operation":{"type":"string","enum":["add","add_dependency","set_state","set_estimate"]},"task_id":{"type":["string","null"]},"description":{"type":["string","null"]},"depends_on":{"type":"array","items":{"type":"string"}},"budget_class":{"type":["string","null"],"enum":["1K","2K","4K","8K","16K","32K","64K","128K",null]},"optimistic_tokens":{"type":"integer","minimum":0},"most_likely_tokens":{"type":"integer","minimum":0},"pessimistic_tokens":{"type":"integer","minimum":0},"state":{"type":["string","null"],"enum":["queued","planning","running","completed","failed","cancelled",null]}}}"""),
+            Define("dir", "Create, remove, or list directories under an approved root. Only empty directories can be removed.", """{"type":"object","additionalProperties":false,"required":["path","operation"],"properties":{"path":{"type":"string"},"operation":{"type":"string","enum":["mkdir","rmdir","list"]}}}""")
         ];
         return definitions.ToDictionary(static definition => definition.Name, StringComparer.Ordinal);
     }
diff --git a/src/Agent.Core/Tools/InternalToolDispatcher.cs b/src/Agent.Core/Tools/InternalToolDispatcher.cs
index 0dca5df..c888705 100644
--- a/src/Agent.Core/Tools/InternalToolDispatcher.cs
+++ b/src/Agent.Core/Tools/InternalToolDispatcher.cs
@@ -23,7 +23,7 @@ public sealed class FakeInternalToolBackend : IInternalToolBackend
     public Task<ToolExecutionResult> ExecuteAsync(Guid taskId, string toolName, JsonElement arguments, CancellationToken cancellationToken)
     {
         _calls.Add((toolName, arguments.Clone()));
-        bool effect = toolName is "file_edit" or "process_run";
+        bool effect = toolName is "file_edit" or "process_run" or "dir";
         return Task.FromResult(new ToolExecutionResult(true, "fake-ok", effect));
     }
 }
diff --git a/src/Agent.Core/Tools/InternalToolValidator.cs b/src/Agent.Core/Tools/InternalToolValidator.cs
index c48719e..091b790 100644
--- a/src/Agent.Core/Tools/InternalToolValidator.cs
+++ b/src/Agent.Core/Tools/InternalToolValidator.cs
@@ -75,6 +75,8 @@ public static class InternalToolValidator
             if (operation == "set_state") Require(arguments, "task_id", "state");
             if (operation == "set_estimate") Require(arguments, "task_id", "budget_class", "optimistic_tokens", "most_likely_tokens", "pessimistic_tokens");
         }
+        // dir: path and operation are already required by the schema; no operation-specific
+        // additional arguments are needed since mkdir/rmdir/list only use the path field.
 
         static void Require(JsonElement value, params string[] properties)
         {