diff --git a/claim.capnp b/claim.capnp
index 8459f33..00d3622 100644
--- a/claim.capnp
+++ b/claim.capnp
@@ -12,6 +12,7 @@ using import "utils.capnp".OID;
 using import "utils.capnp".Map;
 using import "utils.capnp".SturdyRef;
 using import "projects.capnp".Project;
+using import "traits.capnp".Hint;
 
 interface Claimable {
     claim @0 ( project :Project ) -> Fallible(Claim, ClaimError);
diff --git a/interest.capnp b/interest.capnp
index b068b1d..c35e352 100644
--- a/interest.capnp
+++ b/interest.capnp
@@ -25,8 +25,20 @@ interface Interestable {
 interface Interest extends (Owned) {
     resource @0 () -> ( resource :Resource, dummy :UInt8 );
     describe @1 () -> Description;
-    drop @2 ();
-    upgrade @3 () -> ( claim :Claim );
+
+    drop @2 () -> Fallible(DropOk, DropError);
+    struct DropOk {
+
+    }
+    struct DropError {
+
+    }
+
+    upgrade @3 () -> ( claim :Fallible(Claim, UpgradeError) );
+
+    struct UpgradeError {
+
+    }
 }
 
 struct InterestKind {
diff --git a/resource.capnp b/resource.capnp
index 484dc49..02fc9ec 100644
--- a/resource.capnp
+++ b/resource.capnp
@@ -16,6 +16,8 @@ using import "utils.capnp".OID;
 using import "utils.capnp".L10NString;
 using import "utils.capnp".Map;
 
+using import "traits.capnp".Hint;
+
 using import "cache.capnp".Cache;
 
 struct RestoredResource {
@@ -54,6 +56,8 @@ struct Resource {
     # does not support claiming or locking.
 
     audit @6 :Auditable;
+
+    hint @7 :Hint;
 }
 
 struct Description {
diff --git a/traits.capnp b/traits.capnp
index a1b0204..c99545f 100644
--- a/traits.capnp
+++ b/traits.capnp
@@ -1,7 +1,9 @@
 @0xc0542f62613a5c5e;
 
 using CSharp = import "programming_language/csharp.capnp";
-$CSharp.namespace("FabAccessAPI.Schema");
+$CSharp.namespace("FabAccessAPI.Schema"); 
+
+using OID = import "utils.capnp".OID;
 
 interface TraitSuper {
     getName @0 () -> ( name :Text );
@@ -13,3 +15,9 @@ struct TraitError(ConstraintError) {
         constraintViolation @1 :ConstraintError;
     }
 }
+
+interface Hint {
+    getOid @0 () -> ( oid :OID );
+    getAbstract @1 () -> ( abstract :List(Hint) );
+    # Sorted least to most abstract. abstract[0] is the next less specific Hint.
+}
diff --git a/utils.capnp b/utils.capnp
index 231e043..492792f 100644
--- a/utils.capnp
+++ b/utils.capnp
@@ -99,3 +99,8 @@ struct When {
     start @0 :Timestamp;
     end @1 :Timestamp;
 }
+
+struct TreeNode(Value) {
+    value @0 :Value;
+    children @1 :List(TreeNode(Value));
+}