diff --git a/ruma-common/src/thirdparty.rs b/ruma-common/src/thirdparty.rs
index da88c3ae..70c561fa 100644
--- a/ruma-common/src/thirdparty.rs
+++ b/ruma-common/src/thirdparty.rs
@@ -9,7 +9,11 @@ use ruma_identifiers::{RoomAliasId, UserId};
 use serde::{Deserialize, Serialize};
 
 /// Metadata about a third party protocol.
+///
+/// To create an instance of this type, first create a `ProtocolInit` and convert it via
+/// `Protocol::from` / `.into()`.
 #[derive(Clone, Debug, Deserialize, Serialize)]
+#[non_exhaustive]
 pub struct Protocol {
     /// Fields which may be used to identify a third party user.
     pub user_fields: Vec<String>,
@@ -27,8 +31,41 @@ pub struct Protocol {
     pub instances: Vec<ProtocolInstance>,
 }
 
+/// Initial set of fields of `Protocol`.
+///
+/// This struct will not be updated even if additional fields are added to `Prococol` in a new
+/// (non-breaking) release of the Matrix specification.
+#[derive(Debug)]
+pub struct ProtocolInit {
+    /// Fields which may be used to identify a third party user.
+    pub user_fields: Vec<String>,
+
+    /// Fields which may be used to identify a third party location.
+    pub location_fields: Vec<String>,
+
+    /// A content URI representing an icon for the third party protocol.
+    pub icon: String,
+
+    /// The type definitions for the fields defined in `user_fields` and `location_fields`.
+    pub field_types: BTreeMap<String, FieldType>,
+
+    /// A list of objects representing independent instances of configuration.
+    pub instances: Vec<ProtocolInstance>,
+}
+
+impl From<ProtocolInit> for Protocol {
+    fn from(init: ProtocolInit) -> Self {
+        let ProtocolInit { user_fields, location_fields, icon, field_types, instances } = init;
+        Self { user_fields, location_fields, icon, field_types, instances }
+    }
+}
+
 /// Metadata about an instance of a third party protocol.
+///
+/// To create an instance of this type, first create a `ProtocolInstanceInit` and convert it via
+/// `ProtocolInstance::from` / `.into()`.
 #[derive(Clone, Debug, Deserialize, Serialize)]
+#[non_exhaustive]
 pub struct ProtocolInstance {
     /// A human-readable description for the protocol, such as the name.
     pub desc: String,
@@ -44,8 +81,35 @@ pub struct ProtocolInstance {
     pub network_id: String,
 }
 
+/// Initial set of fields of `Protocol`.
+///
+/// This struct will not be updated even if additional fields are added to `Prococol` in a new
+/// (non-breaking) release of the Matrix specification.
+#[derive(Debug)]
+pub struct ProtocolInstanceInit {
+    /// A human-readable description for the protocol, such as the name.
+    pub desc: String,
+
+    /// Preset values for `fields` the client may use to search by.
+    pub fields: BTreeMap<String, String>,
+
+    /// A unique identifier across all instances.
+    pub network_id: String,
+}
+
+impl From<ProtocolInstanceInit> for ProtocolInstance {
+    fn from(init: ProtocolInstanceInit) -> Self {
+        let ProtocolInstanceInit { desc, fields, network_id } = init;
+        Self { desc, icon: None, fields, network_id }
+    }
+}
+
 /// A type definition for a field used to identify third party users or locations.
+///
+/// To create an instance of this type, first create a `FieldTypeInit` and convert it via
+/// `FieldType::from` / `.into()`.
 #[derive(Clone, Debug, Deserialize, Serialize)]
+#[non_exhaustive]
 pub struct FieldType {
     /// A regular expression for validation of a field's value.
     pub regexp: String,
@@ -54,8 +118,29 @@ pub struct FieldType {
     pub placeholder: String,
 }
 
+/// Initial set of fields of `FieldType`.
+///
+/// This struct will not be updated even if additional fields are added to `FieldType` in a new
+/// (non-breaking) release of the Matrix specification.
+#[derive(Debug)]
+pub struct FieldTypeInit {
+    /// A regular expression for validation of a field's value.
+    pub regexp: String,
+
+    /// A placeholder serving as a valid example of the field value.
+    pub placeholder: String,
+}
+
+impl From<FieldTypeInit> for FieldType {
+    fn from(init: FieldTypeInit) -> Self {
+        let FieldTypeInit { regexp, placeholder } = init;
+        Self { regexp, placeholder }
+    }
+}
+
 /// A third party network location.
 #[derive(Clone, Debug, Deserialize, Serialize)]
+#[non_exhaustive]
 pub struct Location {
     /// An alias for a matrix room.
     pub alias: RoomAliasId,
@@ -67,6 +152,13 @@ pub struct Location {
     pub fields: BTreeMap<String, String>,
 }
 
+impl Location {
+    /// Creates a new `Location` with the given alias, protocol and fields.
+    pub fn new(alias: RoomAliasId, protocol: String, fields: BTreeMap<String, String>) -> Self {
+        Self { alias, protocol, fields }
+    }
+}
+
 /// A third party network user.
 #[derive(Clone, Debug, Deserialize, Serialize)]
 pub struct User {
@@ -80,8 +172,16 @@ pub struct User {
     pub fields: BTreeMap<String, String>,
 }
 
+impl User {
+    /// Creates a new `User` with the given userid, protocol and fields.
+    pub fn new(userid: UserId, protocol: String, fields: BTreeMap<String, String>) -> Self {
+        Self { userid, protocol, fields }
+    }
+}
+
 /// The medium of a third party identifier.
 #[derive(Clone, Copy, Debug, PartialEq, Eq, Deserialize, Serialize)]
+#[non_exhaustive]
 #[serde(rename_all = "lowercase")]
 pub enum Medium {
     /// Email address identifier