diff --git a/mintlify/openapi.yaml b/mintlify/openapi.yaml
index d18b3bfa8..40500fd3e 100644
--- a/mintlify/openapi.yaml
+++ b/mintlify/openapi.yaml
@@ -4347,7 +4347,7 @@ paths:
               $ref: '#/components/schemas/CancelTransactionRequest'
       responses:
         '200':
-          description: Cancellation requested successfully
+          description: The banking partner accepted the cancellation request. The transfer reaches its cancelled state once the partner confirms it, so the transaction returned here may still report its pre-cancellation status.
           content:
             application/json:
               schema:
@@ -4382,6 +4382,12 @@ paths:
             application/json:
               schema:
                 $ref: '#/components/schemas/Error500'
+        '501':
+          description: Not implemented for this payment rail. Cancellation depends on the banking partner settling the transfer exposing a cancellation facility; rails without one — wires, and ACH at partners that do not support it — return `501 NOT_IMPLEMENTED`.
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/Error501'
   /crypto/estimate-withdrawal-fee:
     post:
       summary: Estimate crypto withdrawal fee
diff --git a/openapi.yaml b/openapi.yaml
index d18b3bfa8..40500fd3e 100644
--- a/openapi.yaml
+++ b/openapi.yaml
@@ -4347,7 +4347,7 @@ paths:
               $ref: '#/components/schemas/CancelTransactionRequest'
       responses:
         '200':
-          description: Cancellation requested successfully
+          description: The banking partner accepted the cancellation request. The transfer reaches its cancelled state once the partner confirms it, so the transaction returned here may still report its pre-cancellation status.
           content:
             application/json:
               schema:
@@ -4382,6 +4382,12 @@ paths:
             application/json:
               schema:
                 $ref: '#/components/schemas/Error500'
+        '501':
+          description: Not implemented for this payment rail. Cancellation depends on the banking partner settling the transfer exposing a cancellation facility; rails without one — wires, and ACH at partners that do not support it — return `501 NOT_IMPLEMENTED`.
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/Error501'
   /crypto/estimate-withdrawal-fee:
     post:
       summary: Estimate crypto withdrawal fee
diff --git a/openapi/paths/transactions/transactions_{transactionId}_cancel.yaml b/openapi/paths/transactions/transactions_{transactionId}_cancel.yaml
index 7d2899ee5..172f9cb17 100644
--- a/openapi/paths/transactions/transactions_{transactionId}_cancel.yaml
+++ b/openapi/paths/transactions/transactions_{transactionId}_cancel.yaml
@@ -31,7 +31,10 @@ post:
           $ref: ../../components/schemas/transactions/CancelTransactionRequest.yaml
   responses:
     '200':
-      description: Cancellation requested successfully
+      description: >-
+        The banking partner accepted the cancellation request. The transfer
+        reaches its cancelled state once the partner confirms it, so the
+        transaction returned here may still report its pre-cancellation status.
       content:
         application/json:
           schema:
@@ -68,3 +71,13 @@ post:
         application/json:
           schema:
             $ref: ../../components/schemas/errors/Error500.yaml
+    '501':
+      description: >-
+        Not implemented for this payment rail. Cancellation depends on the
+        banking partner settling the transfer exposing a cancellation facility;
+        rails without one — wires, and ACH at partners that do not support it —
+        return `501 NOT_IMPLEMENTED`.
+      content:
+        application/json:
+          schema:
+            $ref: ../../components/schemas/errors/Error501.yaml