diff --git a/catapult/cmd/catapult/make_histogram.go b/catapult/cmd/catapult/make_histogram.go
index cbc677f..f5085d0 100644
--- a/catapult/cmd/catapult/make_histogram.go
+++ b/catapult/cmd/catapult/make_histogram.go
@@ -15,34 +15,92 @@
 	"fuchsia.googlesource.com/testing/catapult"
 	schema "fuchsia.googlesource.com/testing/perf/schema/v1"
 	"github.com/google/subcommands"
+	uuid "github.com/satori/go.uuid"
 )
 
-type MakeHistogramCommand struct{}
+// sharedDiagnostics contains the values to use in the HistogramSet generated
+// by this subcommand.
+//
+// Catapult requires a specific set of shared diagnostics to be present on a
+// HistogramSet before uploading to the dashboard. Those required diagnostics
+// are:
+//
+// * bots - a GenericSet of strings containing bot hostnames
+// * benchmarks - a GenericSet of strings containing Telemetry
+//     benchmark names.
+// * chromiumCommitPositions - a GenericSet of numbers containing
+//     Chromium commit positions.
+// * masters - a GenericSet of strings containing buildbot master hostnames.
+//
+// There are other, optional diagnostics. Those may be added to this struct as
+// needed.
+//
+// Because the names of some diagnostics are not relevant to users of this tool
+// it is ok for this subcommand and this struct to use different names for any
+// of them so long as the names are mapped back to their counterparts when the
+// HistogramSet is constructed.
+//
+// To learn more about Catapult Diagnostics, see:
+// https://github.com/catapult-project/catapult/blob/master/docs/how-to-write-metrics.md
+type sharedDiagnostics struct {
+	// testSuite specifies the test suite that we are creating a
+	// HistogramSet for. e.g. "zircon" "ledger"
+	//
+	// Corresponds to the diagnostic "benchmarks".
+	testSuite string
+
+	// builder specifies the LUCI builder that ran these tests.
+	//
+	// Corresponds to the diagnostic "bots".
+	builder string
+
+	// bucket specifies the LUCI bucket containing the job that ran
+	// these tests.
+	//
+	// Corresponds to the diagnostic "masters".
+	bucket string
+
+	// TODO(kjharland): Add placeholder for chromiumCommitPositions
+	// once the catapult team confirms what we can use this field
+	// for.
+}
+
+type MakeHistogramCommand struct {
+	sharedDiagnostics sharedDiagnostics
+}
 
 func (*MakeHistogramCommand) Name() string {
 	return "make_histogram"
 }
 
 func (*MakeHistogramCommand) Usage() string {
-	return "make_histogram [input_file]"
+	return "make_histogram [options] input_file"
 }
 
 func (*MakeHistogramCommand) Synopsis() string {
 	return "Converts performance test output to a catapult HistogramSet"
 }
 
-func (*MakeHistogramCommand) SetFlags(flags *flag.FlagSet) {}
+func (cmd *MakeHistogramCommand) SetFlags(flags *flag.FlagSet) {
+	flags.StringVar(&cmd.sharedDiagnostics.testSuite, "test-suite", "",
+		"Test suite corresponding to the input file")
+	flags.StringVar(&cmd.sharedDiagnostics.builder, "builder", "",
+		"LUCI builder that generated the test results")
+	flags.StringVar(&cmd.sharedDiagnostics.bucket, "bucket", "",
+		"Buildbucket bucket containing the job that ran the test")
+}
 
-// Execute Converts performance test output to a catapult HistogramSet
+// Execute converts performance test output to a catapult HistogramSet
 // The histogram set created by this command does not contain the necessary
 // diagnostics for sending to catapult.  To add these diagnostics, use:
 //
-// 	$ catapult add_diagnostics ....
+// $ catapult add_diagnostics ....
 //
 // See https://github.com/catapult-project/catapult/blob/master/docs/histogram-set-json-format.md
-func (*MakeHistogramCommand) Execute(ctx context.Context, f *flag.FlagSet, _ ...interface{}) subcommands.ExitStatus {
-	var variants struct {
-		Variants []schema.Variant `json:"variants"`
+func (cmd *MakeHistogramCommand) Execute(ctx context.Context, f *flag.FlagSet, _ ...interface{}) subcommands.ExitStatus {
+	if f.NArg() != 1 {
+		log.Println("missing input_file")
+		return subcommands.ExitFailure
 	}
 
 	inputFile := f.Arg(0)
@@ -52,13 +110,20 @@
 		return subcommands.ExitFailure
 	}
 
+	histogramSet := new(catapult.HistogramSet)
+
+	var variants struct {
+		Variants []schema.Variant `json:"variants"`
+	}
+
 	if err := json.Unmarshal(blob, &variants); err != nil {
 		log.Println(err)
 		return subcommands.ExitFailure
 	}
 
-	histogramSet := catapult.HistogramSet{}
+	// Generate Histograms from test results.
 	histograms := catapult.ConvertVariantsToHistograms(variants.Variants)
+
 	// Track whether any single Histogram addition failed. We do this instead of
 	// exiting after a single error to expose as many errors as possible.
 	anyAddFailed := false
@@ -66,19 +131,41 @@
 		if err := histogramSet.AddHistogram(histogram); err != nil {
 			log.Println(err)
 			anyAddFailed = true
-
 		}
 	}
 	if anyAddFailed {
 		return subcommands.ExitFailure
 	}
 
-	js, err := json.Marshal(&histogramSet)
+	// Add all shared diagnostics, mapping to the appropriate Catapult
+	// diagnostic names.
+	diagnosticInfoPairs := []struct {
+		Name  string
+		Value string
+	}{
+		{"benchmarks", cmd.sharedDiagnostics.testSuite},
+		{"bots", cmd.sharedDiagnostics.builder},
+		{"masters", cmd.sharedDiagnostics.bucket},
+		// Required for uploading, even if value is just empty.
+		{"chromiumCommitPositions", ""},
+	}
+	for _, info := range diagnosticInfoPairs {
+		histogramSet.AddSharedDiagnostic(info.Name, &catapult.GenericSetDiagnostic{
+			Type:   catapult.DiagnosticTypeGenericSet,
+			GUID:   uuid.NewV4().String(),
+			Values: []string{info.Value},
+		})
+	}
+
+	// Serialize and log the new HistogramSet.
+	js, err := json.Marshal(histogramSet.ToJSON())
 	if err != nil {
 		log.Println(err)
 		return subcommands.ExitFailure
 	}
 
+	// TODO(kjharland): Add option to write to a file so this can be used
+	// from a recipe.
 	fmt.Println(string(js))
 	return subcommands.ExitSuccess
 }
diff --git a/catapult/histogram_set.go b/catapult/histogram_set.go
index 1a6f2c6..2858be8 100644
--- a/catapult/histogram_set.go
+++ b/catapult/histogram_set.go
@@ -44,8 +44,11 @@
 	guid := diagnostic.GetGUID()
 
 	// Reference the diagnostic's GUID in each Histogram in this set.
-	for _, histogram := range h.histograms {
-		histogram.AddDiagnostic(name, guid)
+	//
+	// Use the loop index instead of the loop variable since this directly
+	// mutates the histogram.
+	for i := range h.histograms {
+		h.histograms[i].AddDiagnostic(name, guid)
 	}
 }
 
diff --git a/catapult/histogram_set_test.go b/catapult/histogram_set_test.go
index aa93e5a..e324524 100644
--- a/catapult/histogram_set_test.go
+++ b/catapult/histogram_set_test.go
@@ -106,8 +106,10 @@
 			Diagnostics: make(map[string]string),
 		})
 		histogramSet.AddHistogram(catapult.Histogram{
-			Name:        "test_histogram_2",
-			Diagnostics: make(map[string]string),
+			Name: "test_histogram_2",
+			// Intentionally leaving this Diagnostics map as nil to
+			// make sure the map still recieves a reference to the
+			// new Diagnostic.
 		})
 		histogramSet.AddSharedDiagnostic("test_diagnostic", diagnostic)