diff --git a/packages/coordinator-mcp/src/tools.ts b/packages/coordinator-mcp/src/tools.ts
index b1c31a3..c62c04b 100644
--- a/packages/coordinator-mcp/src/tools.ts
+++ b/packages/coordinator-mcp/src/tools.ts
@@ -271,6 +271,10 @@ export interface ToolAnnotations {
  */
 const READ_ONLY = new Set([
   "chap.workspace.describe", "chap.audit.read", "chap.audit.verify_chain", "chap.audit.verify_receipt",
+  // Submitting reads the chain and sends it onward. It changes nothing here,
+  // which is what readOnlyHint claims; openWorldHint carries the fact that it
+  // reaches a service outside this coordinator.
+  "chap.audit.submit_to_scitt",
 ]);
 
 /** Overwrites, removes, or settles state irreversibly. */
diff --git a/packages/coordinator-py/chap_coordinator/transports/mcp_tools.py b/packages/coordinator-py/chap_coordinator/transports/mcp_tools.py
index 1fa3b74..ffccdc0 100644
--- a/packages/coordinator-py/chap_coordinator/transports/mcp_tools.py
+++ b/packages/coordinator-py/chap_coordinator/transports/mcp_tools.py
@@ -356,7 +356,7 @@
     },
     "chap.audit.submit_to_scitt": {
         "title": "Anchor audit log in SCITT",
-        "readOnlyHint": False,
+        "readOnlyHint": True,
         "destructiveHint": False,
         "idempotentHint": False,
         "openWorldHint": True,