diff --git a/pkg/cache/cache.go b/pkg/cache/cache.go
index 3143230..d2808ca 100644
--- a/pkg/cache/cache.go
+++ b/pkg/cache/cache.go
@@ -2,11 +2,13 @@ package cache
 
 import "git.yetaga.in/alazyreader/libyear/pkg/libyear"
 
-// Cache isn't concurrency-safe, but we don't care about that right now
+// Cache holds maps of strings to Info structs.
+// It isn't concurrency-safe, but we don't care about that right now.
 type Cache struct {
 	items map[string]libyear.Info
 }
 
+// Get retrives an Info struct from the cache, if it exists.
 func (c *Cache) Get(k string) libyear.Info {
 	i, ok := c.items[k]
 	if ok {
@@ -15,6 +17,7 @@ func (c *Cache) Get(k string) libyear.Info {
 	return libyear.Info{}
 }
 
+// Set adds an Info struct to the cache.
 func (c *Cache) Set(k string, v libyear.Info) {
 	if c.items == nil {
 		c.items = make(map[string]libyear.Info)
diff --git a/pkg/gomod/gomod.go b/pkg/gomod/gomod.go
index 9f98107..502e517 100644
--- a/pkg/gomod/gomod.go
+++ b/pkg/gomod/gomod.go
@@ -7,26 +7,23 @@ import (
 	"golang.org/x/mod/modfile"
 )
 
-type logger interface {
-	Logf(f string, s ...interface{})
-	Debugf(f string, s ...interface{})
-}
-
+// GoMod represents a Go Modules parser.
+// Running LoadAndComputePairs with a filename will return a slice of parsed dependencies.
 type GoMod struct {
 	IncludeIndirect bool
 	ProxyLoader     Queryer
 	Logger          logger
 }
 
-func isReplaced(module string, replaces []*modfile.Replace) bool {
-	for i := range replaces {
-		if module == replaces[i].Old.Path {
-			return true
-		}
-	}
-	return false
+// logger is an extremely simple leveled logger
+type logger interface {
+	Logf(f string, s ...interface{})
+	Debugf(f string, s ...interface{})
 }
 
+// LoadAndComputePairs takes a filename of a go.mod file,
+// runs the resolution algorithm in the provided Querier,
+// and returns parsed pairs of dependencies and their latest versions.
 func (g *GoMod) LoadAndComputePairs(filename string) ([]libyear.Pair, error) {
 	b, err := os.ReadFile(filename)
 	if err != nil {
@@ -59,3 +56,12 @@ func (g *GoMod) LoadAndComputePairs(filename string) ([]libyear.Pair, error) {
 	}
 	return pairs, nil
 }
+
+func isReplaced(module string, replaces []*modfile.Replace) bool {
+	for i := range replaces {
+		if module == replaces[i].Old.Path {
+			return true
+		}
+	}
+	return false
+}
diff --git a/pkg/gomod/modproxy.go b/pkg/gomod/modproxy.go
index 4e3ce19..02f3be0 100644
--- a/pkg/gomod/modproxy.go
+++ b/pkg/gomod/modproxy.go
@@ -13,6 +13,7 @@ import (
 	"git.yetaga.in/alazyreader/libyear/pkg/libyear"
 )
 
+// A Queryer holds settings for a
 type Queryer struct {
 	Root   string
 	Client http.Client
@@ -25,11 +26,19 @@ type majorVersion struct {
 	version int
 }
 
+// GetLatestVersion returns the "latest" major version of a module,
+// jumping across MVS boundaries:
+// i.e. github.com/foo/bar => github.com/foo/bar/v2 in the case of one version bump
+// github.com/foo/baz/v2 => github.com/foo/baz/v6 in the case of a large jump
+// github.com/foo/quuz/v2 => github.com/foo/quuz/v2 in the case of no jump at all.
 func (q *Queryer) GetLatestVersion(module string) libyear.Info {
 	latestMod := q.findLatestMajorVersion(module)
 	return q.makeProxyRequest(latestMod + "/@latest")
 }
 
+// GetVersion returns the proxy's information about a given version of a module.
+// `module` in this case is a fully-disambiguated MVS name (github.com/foo/bar/v2),
+// and `version` is a version identifier as defined in `https://blog.golang.org/publishing-go-modules#TOC_3.`
 func (q *Queryer) GetVersion(module string, version string) libyear.Info {
 	if !strings.HasPrefix(version, "v") {
 		return libyear.Info{
@@ -44,9 +53,6 @@ func (q *Queryer) GetVersion(module string, version string) libyear.Info {
 }
 
 // given a module, return the "latest" major version of that module, fully defined
-// i.e. github.com/foo/bar => github.com/foo/bar/v2 in the case of one version bump
-// github.com/foo/baz/v2 => github.com/foo/baz/v6 in the case of a large jump
-// github.com/foo/quuz/v2 => github.com/foo/quuz/v2 in the case of no jump at all!
 func (q *Queryer) findLatestMajorVersion(module string) string {
 	for {
 		nextModule := incrementMajorVersion(module)
@@ -58,6 +64,7 @@ func (q *Queryer) findLatestMajorVersion(module string) string {
 	}
 }
 
+// handle calling the go module proxy
 func (q *Queryer) makeProxyRequest(mod string) libyear.Info {
 	if q.Root == "" {
 		q.Root = "https://proxy.golang.org/"
diff --git a/pkg/libyear/libyear.go b/pkg/libyear/libyear.go
index df45587..1173bd3 100644
--- a/pkg/libyear/libyear.go
+++ b/pkg/libyear/libyear.go
@@ -5,17 +5,20 @@ import (
 	"time"
 )
 
+// Info defines a version and a commit time for that version
 type Info struct {
 	Version string    // version string
 	Time    time.Time // commit time
 }
 
+// Pair is a set of versions for a dependency (current and newest possible)
 type Pair struct {
 	Name    string
 	Latest  Info
 	Current Info
 }
 
+// Calc returns the summed time distance (as a time.Duration) between a set of Pairs of modules.
 // TODO: sum can only represent ~290 years before overflowing, but we don't actually need nanosecond precision!
 // Probably worth switching to hour-based summing here.
 func Calc(p ...Pair) time.Duration {
@@ -26,6 +29,7 @@ func Calc(p ...Pair) time.Duration {
 	return sum
 }
 
+// DecimalYear conversts a time.Duration (which is in nsec) to a two-decimal-place count of years.
 func DecimalYear(d time.Duration) string {
 	return fmt.Sprintf("%.2f", float64(d.Truncate(time.Hour)/time.Hour)/float64(8760))
 }
diff --git a/pkg/logger/logger.go b/pkg/logger/logger.go
index 01402ea..4098245 100644
--- a/pkg/logger/logger.go
+++ b/pkg/logger/logger.go
@@ -6,6 +6,7 @@ import (
 	"os"
 )
 
+// Log provices a simple leveled logger
 type Log struct {
 	quiet  bool
 	debug  bool
@@ -13,6 +14,7 @@ type Log struct {
 	stdOut io.Writer
 }
 
+// NewLogger returns a new logger (duh) with the given levels and output writers
 func NewLogger(quiet, debug bool, stdOut, errOut io.Writer) *Log {
 	if stdOut == nil {
 		stdOut = os.Stdout
@@ -28,32 +30,38 @@ func NewLogger(quiet, debug bool, stdOut, errOut io.Writer) *Log {
 	}
 }
 
+// Error logs at the error level
 func (l *Log) Error(s ...interface{}) {
 	fmt.Fprint(l.errOut, s...)
 }
 
+// Errorf uses fmt.Fprint formatting
 func (l *Log) Errorf(f string, s ...interface{}) {
-	fmt.Fprint(l.errOut, s...)
+	fmt.Fprintf(l.errOut, f, s...)
 }
 
+// Log only logs if quiet is false
 func (l *Log) Log(s ...interface{}) {
 	if !l.quiet {
 		fmt.Fprint(l.stdOut, s...)
 	}
 }
 
+// Logf uses fmt.Fprint fprmatting
 func (l *Log) Logf(f string, s ...interface{}) {
 	if !l.quiet {
 		fmt.Fprintf(l.stdOut, f, s...)
 	}
 }
 
+// Debug logs debug-level logs if debug is true
 func (l *Log) Debug(s ...interface{}) {
 	if l.debug {
 		fmt.Fprint(l.errOut, s...)
 	}
 }
 
+// Debugf uses fmt.Fprint fprmatting
 func (l *Log) Debugf(f string, s ...interface{}) {
 	if l.debug {
 		fmt.Fprintf(l.errOut, f, s...)