diff --git a/builtin.aqua b/builtin.aqua
index 6345201..2a2a223 100644
--- a/builtin.aqua
+++ b/builtin.aqua
@@ -254,17 +254,32 @@ service Script("script"):
     -- Each object in the list is of the following structure
     list() -> []ScriptInfo
 
+data SignResult:
+    -- Was call successful or not
+    success: bool
+    -- Error message. Will be null if the call is successful
+    error: ?string
+    -- Signature as byte array. Will be null if the call is not successful
+    signature: ?[]u8
+
+-- Available only on FluenceJS peers
+-- The service can also be resolved by it's host peer id
 service Sig("sig"):
-    -- Signs data with the current peer's key. 
-    -- Can only be called on %init_peer_id%
-    -- Accepts data only from the following sources:
+    -- Signs data with the service's private key. 
+    -- Depending on implementation the service might check call params to restrict usage for security reasons.
+    -- By default it is only allowed to be used on the same peer the particle was initiated
+    -- and accepts data only from the following sources:
     --   trust-graph.get_trust_bytes
     --   trust-graph.get_revocation_bytes
     --   registry.get_key_bytes
     --   registry.get_record_bytes
+    --   registry.get_host_record_bytes
     -- Argument: data - byte array to sign
-    -- Returns: signature as a byte array
-    sign(data: []u8) -> []u8
+    -- Returns: signature as SignResult structure
+    sign(data: []u8) -> SignResult
 
--- Given the data and signature both as byte arrays, returns true if the signature is correct, false otherwise.
+    -- Given the data and signature both as byte arrays, returns true if the signature is correct, false otherwise.
     verify(signature: []u8, data: []u8) -> bool
+
+    -- Gets service's public key.
+    get_pub_key() -> string