diff --git a/edm4eic.yaml b/edm4eic.yaml
index dfaa144..39b0fdc 100644
--- a/edm4eic.yaml
+++ b/edm4eic.yaml
@@ -200,6 +200,13 @@ components:
       - bool     TOTInProgress      // Flag which indicates if TOT calculation is ongoing, ADC value may be corrupted if this is true
       - bool     TOTComplete        // Flag which indicates if a TOT calculation is complete and TOT value is valid
 
+  ## Event-level truthiness information
+  edm4eic::TruthinessContribution:
+    Members:
+      - float pid                 // Contribution of PID matching to truthiness
+      - float energy              // Contribution of energy matching to truthiness
+      - float momentum            // Contribution of momentum matching to truthiness
+
 datatypes:
 
   edm4eic::Tensor:
@@ -540,7 +547,7 @@ datatypes:
       - edm4eic::ReconstructedParticle hadrons // Reconstructed hadrons used in calculation
 
   ## ==========================================================================
-  ## Data-Montecarlo relations
+  ## Data-Monte Carlo relations
   ## ==========================================================================
 
   edm4eic::MCRecoParticleAssociation:
@@ -623,6 +630,27 @@ datatypes:
       - edm4eic::Track        from   // reference to the track
       - edm4eic::ProtoCluster to     // reference to the protocluster
 
+  ## ==========================================================================
+  ## Data-Monte Carlo comparisons
+  ## ==========================================================================
+
+  edm4eic::Truthiness:
+    Description: "Positive-definite convex norm of how confidently wrong the reconstruction is,
+                  with non-negative contributions from various aspects of the reconstruction,
+                  where a zero value indicates a perfect reconstruction."
+    Author: "W. Deconinck, S. Colbert"
+    Members:
+       - float truthiness                                         // Overall truthiness of the entire event
+       - edm4eic::TruthinessContribution associationContribution  // Contribution from all associated particles
+       - float unassociatedMCParticlesContribution                // Contribution from unassociated MC particles
+       - float unassociatedRecoParticlesContribution              // Contribution from unassociated reconstructed particles
+    VectorMembers:
+      - edm4eic::TruthinessContribution associationContributions  // Contribution from associated particles
+    OneToManyRelations:
+       - edm4eic::MCRecoParticleAssociation associations          // Reference to the associated particles
+       - edm4hep::MCParticle unassociatedMCParticles              // Reference to the unassociated MC particles
+       - edm4eic::ReconstructedParticle unassociatedRecoParticles // Reference to the unassociated reconstructed particles
+
 links:
   edm4eic::TrackProtoClusterLink:
     Description: "Link between a ProtoCluster and a Track"