diff --git a/cstool/README b/cstool/README
index 65479cbc..71c21f8d 100644
--- a/cstool/README
+++ b/cstool/README
@@ -22,5 +22,21 @@ inputs have the same output with the example above.
 	$ cstool x32 "90+91"
 	$ cstool x32 "90:91"
 
-To see all the supported options, run ./cstool
+To print out instruction details, run Cstool with -d option, like below.
 
+	$ cstool -d x32 "01 d8"
+	0  01d8                              add	eax, ebx
+		Prefix:0x00 0x00 0x00 0x00
+		Opcode:0x01 0x00 0x00 0x00
+		rex: 0x0
+		addr_size: 4
+		modrm: 0xd8
+		disp: 0x0
+		sib: 0x0
+		op_count: 2
+			operands[0].type: REG = eax
+			operands[0].size: 4
+			operands[1].type: REG = ebx
+			operands[1].size: 4
+
+To see all the supported options, run ./cstool