diff --git a/action.go b/action.go
index 5bdc7de0..e19493b9 100644
--- a/action.go
+++ b/action.go
@@ -74,8 +74,12 @@ func (s *ActionsServiceOp) List(opt *ListOptions) ([]Action, *Response, error) {
 	return root.Actions, resp, err
 }
 
-// Get an action by ID
+// Get an action by ID.
 func (s *ActionsServiceOp) Get(id int) (*Action, *Response, error) {
+	if id < 1 {
+		return nil, nil, NewArgError("id", "cannot be less than 1")
+	}
+
 	path := fmt.Sprintf("%s/%d", actionsBasePath, id)
 	req, err := s.client.NewRequest("GET", path, nil)
 	if err != nil {
diff --git a/domains.go b/domains.go
index 4860092c..31de1786 100644
--- a/domains.go
+++ b/domains.go
@@ -87,7 +87,7 @@ func (d Domain) String() string {
 	return Stringify(d)
 }
 
-// List all domains
+// List all domains.
 func (s DomainsServiceOp) List(opt *ListOptions) ([]Domain, *Response, error) {
 	path := domainsBasePath
 	path, err := addOptions(path, opt)
@@ -112,8 +112,12 @@ func (s DomainsServiceOp) List(opt *ListOptions) ([]Domain, *Response, error) {
 	return root.Domains, resp, err
 }
 
-// Get individual domain
+// Get individual domain. It requires a non-empty domain name.
 func (s *DomainsServiceOp) Get(name string) (*Domain, *Response, error) {
+	if len(name) < 1 {
+		return nil, nil, NewArgError("name", "cannot be an empty string")
+	}
+
 	path := fmt.Sprintf("%s/%s", domainsBasePath, name)
 
 	req, err := s.client.NewRequest("GET", path, nil)
@@ -132,6 +136,10 @@ func (s *DomainsServiceOp) Get(name string) (*Domain, *Response, error) {
 
 // Create a new domain
 func (s *DomainsServiceOp) Create(createRequest *DomainCreateRequest) (*Domain, *Response, error) {
+	if createRequest == nil {
+		return nil, nil, NewArgError("createRequest", "cannot be nil")
+	}
+
 	path := domainsBasePath
 
 	req, err := s.client.NewRequest("POST", path, createRequest)
@@ -149,6 +157,10 @@ func (s *DomainsServiceOp) Create(createRequest *DomainCreateRequest) (*Domain,
 
 // Delete domain
 func (s *DomainsServiceOp) Delete(name string) (*Response, error) {
+	if len(name) < 1 {
+		return nil, NewArgError("name", "cannot be an empty string")
+	}
+
 	path := fmt.Sprintf("%s/%s", domainsBasePath, name)
 
 	req, err := s.client.NewRequest("DELETE", path, nil)
@@ -173,6 +185,10 @@ func (d DomainRecordEditRequest) String() string {
 
 // Records returns a slice of DomainRecords for a domain
 func (s *DomainsServiceOp) Records(domain string, opt *ListOptions) ([]DomainRecord, *Response, error) {
+	if len(domain) < 1 {
+		return nil, nil, NewArgError("domain", "cannot be an empty string")
+	}
+
 	path := fmt.Sprintf("%s/%s/records", domainsBasePath, domain)
 	path, err := addOptions(path, opt)
 	if err != nil {
@@ -198,6 +214,14 @@ func (s *DomainsServiceOp) Records(domain string, opt *ListOptions) ([]DomainRec
 
 // Record returns the record id from a domain
 func (s *DomainsServiceOp) Record(domain string, id int) (*DomainRecord, *Response, error) {
+	if len(domain) < 1 {
+		return nil, nil, NewArgError("domain", "cannot be an empty string")
+	}
+
+	if id < 1 {
+		return nil, nil, NewArgError("id", "cannot be less than 1")
+	}
+
 	path := fmt.Sprintf("%s/%s/records/%d", domainsBasePath, domain, id)
 
 	req, err := s.client.NewRequest("GET", path, nil)
@@ -216,6 +240,14 @@ func (s *DomainsServiceOp) Record(domain string, id int) (*DomainRecord, *Respon
 
 // DeleteRecord deletes a record from a domain identified by id
 func (s *DomainsServiceOp) DeleteRecord(domain string, id int) (*Response, error) {
+	if len(domain) < 1 {
+		return nil, NewArgError("domain", "cannot be an empty string")
+	}
+
+	if id < 1 {
+		return nil, NewArgError("id", "cannot be less than 1")
+	}
+
 	path := fmt.Sprintf("%s/%s/records/%d", domainsBasePath, domain, id)
 
 	req, err := s.client.NewRequest("DELETE", path, nil)
@@ -232,7 +264,20 @@ func (s *DomainsServiceOp) DeleteRecord(domain string, id int) (*Response, error
 func (s *DomainsServiceOp) EditRecord(
 	domain string,
 	id int,
-	editRequest *DomainRecordEditRequest) (*DomainRecord, *Response, error) {
+	editRequest *DomainRecordEditRequest,
+) (*DomainRecord, *Response, error) {
+	if len(domain) < 1 {
+		return nil, nil, NewArgError("domain", "cannot be an empty string")
+	}
+
+	if id < 1 {
+		return nil, nil, NewArgError("id", "cannot be less than 1")
+	}
+
+	if editRequest == nil {
+		return nil, nil, NewArgError("editRequest", "cannot be nil")
+	}
+
 	path := fmt.Sprintf("%s/%s/records/%d", domainsBasePath, domain, id)
 
 	req, err := s.client.NewRequest("PUT", path, editRequest)
@@ -253,6 +298,14 @@ func (s *DomainsServiceOp) EditRecord(
 func (s *DomainsServiceOp) CreateRecord(
 	domain string,
 	createRequest *DomainRecordEditRequest) (*DomainRecord, *Response, error) {
+	if len(domain) < 1 {
+		return nil, nil, NewArgError("domain", "cannot be empty string")
+	}
+
+	if createRequest == nil {
+		return nil, nil, NewArgError("createRequest", "cannot be nil")
+	}
+
 	path := fmt.Sprintf("%s/%s/records", domainsBasePath, domain)
 	req, err := s.client.NewRequest("POST", path, createRequest)
 
diff --git a/droplet_actions.go b/droplet_actions.go
index 17b53c29..7c9c3fbc 100644
--- a/droplet_actions.go
+++ b/droplet_actions.go
@@ -161,6 +161,14 @@ func (s *DropletActionsServiceOp) Upgrade(id int) (*Action, *Response, error) {
 }
 
 func (s *DropletActionsServiceOp) doAction(id int, request *ActionRequest) (*Action, *Response, error) {
+	if id < 1 {
+		return nil, nil, NewArgError("id", "cannot be less than 1")
+	}
+
+	if request == nil {
+		return nil, nil, NewArgError("request", "request can't be nil")
+	}
+
 	path := dropletActionPath(id)
 
 	req, err := s.client.NewRequest("POST", path, request)
@@ -179,6 +187,14 @@ func (s *DropletActionsServiceOp) doAction(id int, request *ActionRequest) (*Act
 
 // Get an action for a particular droplet by id.
 func (s *DropletActionsServiceOp) Get(dropletID, actionID int) (*Action, *Response, error) {
+	if dropletID < 1 {
+		return nil, nil, NewArgError("dropletID", "cannot be less than 1")
+	}
+
+	if actionID < 1 {
+		return nil, nil, NewArgError("actionID", "cannot be less than 1")
+	}
+
 	path := fmt.Sprintf("%s/%d", dropletActionPath(dropletID), actionID)
 	return s.get(path)
 }
diff --git a/droplets.go b/droplets.go
index 0ac48748..696d6210 100644
--- a/droplets.go
+++ b/droplets.go
@@ -194,6 +194,10 @@ func (s *DropletsServiceOp) List(opt *ListOptions) ([]Droplet, *Response, error)
 
 // Get individual droplet
 func (s *DropletsServiceOp) Get(dropletID int) (*Droplet, *Response, error) {
+	if dropletID < 1 {
+		return nil, nil, NewArgError("dropletID", "cannot be less than 1")
+	}
+
 	path := fmt.Sprintf("%s/%d", dropletBasePath, dropletID)
 
 	req, err := s.client.NewRequest("GET", path, nil)
@@ -212,6 +216,10 @@ func (s *DropletsServiceOp) Get(dropletID int) (*Droplet, *Response, error) {
 
 // Create droplet
 func (s *DropletsServiceOp) Create(createRequest *DropletCreateRequest) (*Droplet, *Response, error) {
+	if createRequest == nil {
+		return nil, nil, NewArgError("createRequest", "cannot be nil")
+	}
+
 	path := dropletBasePath
 
 	req, err := s.client.NewRequest("POST", path, createRequest)
@@ -233,6 +241,10 @@ func (s *DropletsServiceOp) Create(createRequest *DropletCreateRequest) (*Drople
 
 // Delete droplet
 func (s *DropletsServiceOp) Delete(dropletID int) (*Response, error) {
+	if dropletID < 1 {
+		return nil, NewArgError("dropletID", "cannot be less than 1")
+	}
+
 	path := fmt.Sprintf("%s/%d", dropletBasePath, dropletID)
 
 	req, err := s.client.NewRequest("DELETE", path, nil)
@@ -247,6 +259,10 @@ func (s *DropletsServiceOp) Delete(dropletID int) (*Response, error) {
 
 // Kernels lists kernels available for a droplet.
 func (s *DropletsServiceOp) Kernels(dropletID int, opt *ListOptions) ([]Kernel, *Response, error) {
+	if dropletID < 1 {
+		return nil, nil, NewArgError("dropletID", "cannot be less than 1")
+	}
+
 	path := fmt.Sprintf("%s/%d/kernels", dropletBasePath, dropletID)
 	path, err := addOptions(path, opt)
 	if err != nil {
@@ -269,6 +285,10 @@ func (s *DropletsServiceOp) Kernels(dropletID int, opt *ListOptions) ([]Kernel,
 
 // Actions lists the actions for a droplet.
 func (s *DropletsServiceOp) Actions(dropletID int, opt *ListOptions) ([]Action, *Response, error) {
+	if dropletID < 1 {
+		return nil, nil, NewArgError("dropletID", "cannot be less than 1")
+	}
+
 	path := fmt.Sprintf("%s/%d/actions", dropletBasePath, dropletID)
 	path, err := addOptions(path, opt)
 	if err != nil {
@@ -294,6 +314,10 @@ func (s *DropletsServiceOp) Actions(dropletID int, opt *ListOptions) ([]Action,
 
 // Backups lists the backups for a droplet.
 func (s *DropletsServiceOp) Backups(dropletID int, opt *ListOptions) ([]Image, *Response, error) {
+	if dropletID < 1 {
+		return nil, nil, NewArgError("dropletID", "cannot be less than 1")
+	}
+
 	path := fmt.Sprintf("%s/%d/backups", dropletBasePath, dropletID)
 	path, err := addOptions(path, opt)
 	if err != nil {
@@ -319,6 +343,10 @@ func (s *DropletsServiceOp) Backups(dropletID int, opt *ListOptions) ([]Image, *
 
 // Snapshots lists the snapshots available for a droplet.
 func (s *DropletsServiceOp) Snapshots(dropletID int, opt *ListOptions) ([]Image, *Response, error) {
+	if dropletID < 1 {
+		return nil, nil, NewArgError("dropletID", "cannot be less than 1")
+	}
+
 	path := fmt.Sprintf("%s/%d/snapshots", dropletBasePath, dropletID)
 	path, err := addOptions(path, opt)
 	if err != nil {
@@ -344,6 +372,10 @@ func (s *DropletsServiceOp) Snapshots(dropletID int, opt *ListOptions) ([]Image,
 
 // Neighbors lists the neighbors for a droplet.
 func (s *DropletsServiceOp) Neighbors(dropletID int) ([]Droplet, *Response, error) {
+	if dropletID < 1 {
+		return nil, nil, NewArgError("dropletID", "cannot be less than 1")
+	}
+
 	path := fmt.Sprintf("%s/%d/neighbors", dropletBasePath, dropletID)
 
 	req, err := s.client.NewRequest("GET", path, nil)
diff --git a/errors.go b/errors.go
new file mode 100644
index 00000000..a65ebd76
--- /dev/null
+++ b/errors.go
@@ -0,0 +1,24 @@
+package godo
+
+import "fmt"
+
+// ArgError is an error that represents an error with an input to godo. It
+// identifies the argument and the cause (if possible).
+type ArgError struct {
+	arg    string
+	reason string
+}
+
+var _ error = &ArgError{}
+
+// NewArgError creates an InputError.
+func NewArgError(arg, reason string) *ArgError {
+	return &ArgError{
+		arg:    arg,
+		reason: reason,
+	}
+}
+
+func (e *ArgError) Error() string {
+	return fmt.Sprintf("%s is invalid because %s", e.arg, e.reason)
+}
diff --git a/errors_test.go b/errors_test.go
new file mode 100644
index 00000000..71bf1edc
--- /dev/null
+++ b/errors_test.go
@@ -0,0 +1,11 @@
+package godo
+
+import "testing"
+
+func TestArgError(t *testing.T) {
+	expected := "foo is invalid because bar"
+	err := NewArgError("foo", "bar")
+	if got := err.Error(); got != expected {
+		t.Errorf("ArgError().Error() = %q; expected %q", got, expected)
+	}
+}
diff --git a/image_actions.go b/image_actions.go
index 89a9d173..2d053856 100644
--- a/image_actions.go
+++ b/image_actions.go
@@ -20,6 +20,14 @@ var _ ImageActionsService = &ImageActionsServiceOp{}
 
 // Transfer an image
 func (i *ImageActionsServiceOp) Transfer(imageID int, transferRequest *ActionRequest) (*Action, *Response, error) {
+	if imageID < 1 {
+		return nil, nil, NewArgError("imageID", "cannot be less than 1")
+	}
+
+	if transferRequest == nil {
+		return nil, nil, NewArgError("transferRequest", "cannot be nil")
+	}
+
 	path := fmt.Sprintf("v2/images/%d/actions", imageID)
 
 	req, err := i.client.NewRequest("POST", path, transferRequest)
@@ -38,6 +46,14 @@ func (i *ImageActionsServiceOp) Transfer(imageID int, transferRequest *ActionReq
 
 // Get an action for a particular image by id.
 func (i *ImageActionsServiceOp) Get(imageID, actionID int) (*Action, *Response, error) {
+	if imageID < 1 {
+		return nil, nil, NewArgError("imageID", "cannot be less than 1")
+	}
+
+	if actionID < 1 {
+		return nil, nil, NewArgError("actionID", "cannot be less than 1")
+	}
+
 	path := fmt.Sprintf("v2/images/%d/actions/%d", imageID, actionID)
 
 	req, err := i.client.NewRequest("GET", path, nil)
diff --git a/images.go b/images.go
index 7acee84e..96894f88 100644
--- a/images.go
+++ b/images.go
@@ -87,16 +87,32 @@ func (s *ImagesServiceOp) ListUser(opt *ListOptions) ([]Image, *Response, error)
 
 // GetByID retrieves an image by id.
 func (s *ImagesServiceOp) GetByID(imageID int) (*Image, *Response, error) {
+	if imageID < 1 {
+		return nil, nil, NewArgError("imageID", "cannot be less than 1")
+	}
+
 	return s.get(interface{}(imageID))
 }
 
 // GetBySlug retrieves an image by slug.
 func (s *ImagesServiceOp) GetBySlug(slug string) (*Image, *Response, error) {
+	if len(slug) < 1 {
+		return nil, nil, NewArgError("slug", "cannot be blank")
+	}
+
 	return s.get(interface{}(slug))
 }
 
 // Update an image name.
 func (s *ImagesServiceOp) Update(imageID int, updateRequest *ImageUpdateRequest) (*Image, *Response, error) {
+	if imageID < 1 {
+		return nil, nil, NewArgError("imageID", "cannot be less than 1")
+	}
+
+	if updateRequest == nil {
+		return nil, nil, NewArgError("updateRequest", "cannot be nil")
+	}
+
 	path := fmt.Sprintf("%s/%d", imageBasePath, imageID)
 	req, err := s.client.NewRequest("PUT", path, updateRequest)
 	if err != nil {
@@ -114,6 +130,10 @@ func (s *ImagesServiceOp) Update(imageID int, updateRequest *ImageUpdateRequest)
 
 // Delete an image.
 func (s *ImagesServiceOp) Delete(imageID int) (*Response, error) {
+	if imageID < 1 {
+		return nil, NewArgError("imageID", "cannot be less than 1")
+	}
+
 	path := fmt.Sprintf("%s/%d", imageBasePath, imageID)
 
 	req, err := s.client.NewRequest("DELETE", path, nil)
diff --git a/keys.go b/keys.go
index b6e5c412..8dc50f8a 100644
--- a/keys.go
+++ b/keys.go
@@ -101,18 +101,30 @@ func (s *KeysServiceOp) get(path string) (*Key, *Response, error) {
 
 // GetByID gets a Key by id
 func (s *KeysServiceOp) GetByID(keyID int) (*Key, *Response, error) {
+	if keyID < 1 {
+		return nil, nil, NewArgError("keyID", "cannot be less than 1")
+	}
+
 	path := fmt.Sprintf("%s/%d", keysBasePath, keyID)
 	return s.get(path)
 }
 
 // GetByFingerprint gets a Key by by fingerprint
 func (s *KeysServiceOp) GetByFingerprint(fingerprint string) (*Key, *Response, error) {
+	if len(fingerprint) < 1 {
+		return nil, nil, NewArgError("fingerprint", "cannot not be empty")
+	}
+
 	path := fmt.Sprintf("%s/%s", keysBasePath, fingerprint)
 	return s.get(path)
 }
 
 // Create a key using a KeyCreateRequest
 func (s *KeysServiceOp) Create(createRequest *KeyCreateRequest) (*Key, *Response, error) {
+	if createRequest == nil {
+		return nil, nil, NewArgError("createRequest", "cannot be nil")
+	}
+
 	req, err := s.client.NewRequest("POST", keysBasePath, createRequest)
 	if err != nil {
 		return nil, nil, err
@@ -129,6 +141,14 @@ func (s *KeysServiceOp) Create(createRequest *KeyCreateRequest) (*Key, *Response
 
 // UpdateByID updates a key name by ID.
 func (s *KeysServiceOp) UpdateByID(keyID int, updateRequest *KeyUpdateRequest) (*Key, *Response, error) {
+	if keyID < 1 {
+		return nil, nil, NewArgError("keyID", "cannot be less than 1")
+	}
+
+	if updateRequest == nil {
+		return nil, nil, NewArgError("updateRequest", "cannot be nil")
+	}
+
 	path := fmt.Sprintf("%s/%d", keysBasePath, keyID)
 	req, err := s.client.NewRequest("PUT", path, updateRequest)
 	if err != nil {
@@ -146,6 +166,14 @@ func (s *KeysServiceOp) UpdateByID(keyID int, updateRequest *KeyUpdateRequest) (
 
 // UpdateByFingerprint updates a key name by fingerprint.
 func (s *KeysServiceOp) UpdateByFingerprint(fingerprint string, updateRequest *KeyUpdateRequest) (*Key, *Response, error) {
+	if len(fingerprint) < 1 {
+		return nil, nil, NewArgError("fingerprint", "cannot be empty")
+	}
+
+	if updateRequest == nil {
+		return nil, nil, NewArgError("updateRequest", "cannot be nil")
+	}
+
 	path := fmt.Sprintf("%s/%s", keysBasePath, fingerprint)
 	req, err := s.client.NewRequest("PUT", path, updateRequest)
 	if err != nil {
@@ -175,12 +203,20 @@ func (s *KeysServiceOp) delete(path string) (*Response, error) {
 
 // DeleteByID deletes a key by its id
 func (s *KeysServiceOp) DeleteByID(keyID int) (*Response, error) {
+	if keyID < 1 {
+		return nil, NewArgError("keyID", "cannot be less than 1")
+	}
+
 	path := fmt.Sprintf("%s/%d", keysBasePath, keyID)
 	return s.delete(path)
 }
 
 // DeleteByFingerprint deletes a key by its fingerprint
 func (s *KeysServiceOp) DeleteByFingerprint(fingerprint string) (*Response, error) {
+	if len(fingerprint) < 1 {
+		return nil, NewArgError("fingerprint", "cannot be empty")
+	}
+
 	path := fmt.Sprintf("%s/%s", keysBasePath, fingerprint)
 	return s.delete(path)
 }