diff --git a/cmd/callgraph/main.go b/cmd/callgraph/main.go
index 57ad2dd7..0c381b91 100644
--- a/cmd/callgraph/main.go
+++ b/cmd/callgraph/main.go
@@ -134,7 +134,7 @@ func init() {
 func main() {
 	flag.Parse()
 	if err := doCallgraph(&build.Default, *algoFlag, *formatFlag, *testFlag, flag.Args()); err != nil {
-		fmt.Fprintf(os.Stderr, "callgraph: %s.\n", err)
+		fmt.Fprintf(os.Stderr, "callgraph: %s\n", err)
 		os.Exit(1)
 	}
 }
diff --git a/cmd/digraph/digraph.go b/cmd/digraph/digraph.go
index 76d39ec0..89855a90 100644
--- a/cmd/digraph/digraph.go
+++ b/cmd/digraph/digraph.go
@@ -98,7 +98,7 @@ func main() {
 	}
 
 	if err := digraph(args[0], args[1:]); err != nil {
-		fmt.Fprintf(os.Stderr, "Error: %s\n", err)
+		fmt.Fprintf(os.Stderr, "digraph: %s\n", err)
 		os.Exit(1)
 	}
 }
@@ -265,7 +265,7 @@ func digraph(cmd string, args []string) error {
 	switch cmd {
 	case "nodes":
 		if len(args) != 0 {
-			return fmt.Errorf("usage: nodes")
+			return fmt.Errorf("usage: digraph nodes")
 		}
 		nodes := make(nodeset)
 		for label := range g {
@@ -275,7 +275,7 @@ func digraph(cmd string, args []string) error {
 
 	case "degree":
 		if len(args) != 0 {
-			return fmt.Errorf("usage: degree")
+			return fmt.Errorf("usage: digraph degree")
 		}
 		nodes := make(nodeset)
 		for label := range g {
@@ -288,7 +288,7 @@ func digraph(cmd string, args []string) error {
 
 	case "succs", "preds":
 		if len(args) == 0 {
-			return fmt.Errorf("usage: %s <label> ...", cmd)
+			return fmt.Errorf("usage: digraph %s <label> ...", cmd)
 		}
 		g := g
 		if cmd == "preds" {
@@ -306,7 +306,7 @@ func digraph(cmd string, args []string) error {
 
 	case "forward", "reverse":
 		if len(args) == 0 {
-			return fmt.Errorf("usage: %s <label> ...", cmd)
+			return fmt.Errorf("usage: digraph %s <label> ...", cmd)
 		}
 		roots := make(nodeset)
 		for _, root := range args {
@@ -323,7 +323,7 @@ func digraph(cmd string, args []string) error {
 
 	case "somepath":
 		if len(args) != 2 {
-			return fmt.Errorf("usage: somepath <from> <to>")
+			return fmt.Errorf("usage: digraph somepath <from> <to>")
 		}
 		from, to := args[0], args[1]
 		if g[from] == nil {
@@ -356,7 +356,7 @@ func digraph(cmd string, args []string) error {
 
 	case "allpaths":
 		if len(args) != 2 {
-			return fmt.Errorf("usage: allpaths <from> <to>")
+			return fmt.Errorf("usage: digraph allpaths <from> <to>")
 		}
 		from, to := args[0], args[1]
 		if g[from] == nil {
@@ -395,7 +395,7 @@ func digraph(cmd string, args []string) error {
 
 	case "sccs":
 		if len(args) != 0 {
-			return fmt.Errorf("usage: sccs")
+			return fmt.Errorf("usage: digraph sccs")
 		}
 		for _, scc := range g.sccs() {
 			scc.sort().println(" ")
@@ -403,7 +403,7 @@ func digraph(cmd string, args []string) error {
 
 	case "scc":
 		if len(args) != 1 {
-			return fmt.Errorf("usage: scc <label>")
+			return fmt.Errorf("usage: digraph scc <label>")
 		}
 		label := args[0]
 		if g[label] == nil {
diff --git a/cmd/eg/eg.go b/cmd/eg/eg.go
index 8d2342ab..ed7fb530 100644
--- a/cmd/eg/eg.go
+++ b/cmd/eg/eg.go
@@ -11,7 +11,6 @@ import (
 	"go/token"
 	"os"
 	"os/exec"
-	"path/filepath"
 	"strings"
 
 	"golang.org/x/tools/go/loader"
@@ -37,7 +36,7 @@ Usage: eg -t template.go [-w] [-transitive] <args>...
 
 func main() {
 	if err := doMain(); err != nil {
-		fmt.Fprintf(os.Stderr, "%s: %s.\n", filepath.Base(os.Args[0]), err)
+		fmt.Fprintf(os.Stderr, "eg: %s\n", err)
 		os.Exit(1)
 	}
 }
@@ -128,7 +127,7 @@ func doMain() error {
 					}
 				}
 				if err := eg.WriteAST(iprog.Fset, filename, file); err != nil {
-					fmt.Fprintf(os.Stderr, "Error: %s\n", err)
+					fmt.Fprintf(os.Stderr, "eg: %s\n", err)
 					hadErrors = true
 				}
 			} else {
diff --git a/cmd/gorename/main.go b/cmd/gorename/main.go
index 20e271ea..b2ce7b5b 100644
--- a/cmd/gorename/main.go
+++ b/cmd/gorename/main.go
@@ -120,7 +120,7 @@ Features:
 func main() {
 	flag.Parse()
 	if len(flag.Args()) > 0 {
-		fmt.Fprintf(os.Stderr, "Error: surplus arguments.\n")
+		fmt.Fprintln(os.Stderr, "gorename: surplus arguments.")
 		os.Exit(1)
 	}
 
@@ -131,7 +131,7 @@ func main() {
 
 	if err := rename.Main(&build.Default, *offsetFlag, *fromFlag, *toFlag); err != nil {
 		if err != rename.ConflictError {
-			fmt.Fprintf(os.Stderr, "Error: %s.\n", err)
+			fmt.Fprintf(os.Stderr, "gorename: %s\n", err)
 		}
 		os.Exit(1)
 	}
diff --git a/cmd/ssadump/main.go b/cmd/ssadump/main.go
index f0636596..91445213 100644
--- a/cmd/ssadump/main.go
+++ b/cmd/ssadump/main.go
@@ -74,7 +74,7 @@ func init() {
 
 func main() {
 	if err := doMain(); err != nil {
-		fmt.Fprintf(os.Stderr, "ssadump: %s.\n", err)
+		fmt.Fprintf(os.Stderr, "ssadump: %s\n", err)
 		os.Exit(1)
 	}
 }
diff --git a/refactor/rename/rename.go b/refactor/rename/rename.go
index 25e1071b..f03bd10a 100644
--- a/refactor/rename/rename.go
+++ b/refactor/rename/rename.go
@@ -281,7 +281,7 @@ func (r *renamer) update() error {
 					}
 				}
 				if err := rewriteFile(r.iprog.Fset, f, tokenFile.Name()); err != nil {
-					fmt.Fprintf(os.Stderr, "Error: %s.\n", err)
+					fmt.Fprintf(os.Stderr, "gorename: %s\n", err)
 					nerrs++
 				}
 			}