diff --git a/pkgs/clan-cli/clan_cli/api/modules.py b/pkgs/clan-cli/clan_cli/api/modules.py
index 290689bf4..0812c89c5 100644
--- a/pkgs/clan-cli/clan_cli/api/modules.py
+++ b/pkgs/clan-cli/clan_cli/api/modules.py
@@ -3,13 +3,16 @@ import re
 import tomllib
 from dataclasses import dataclass
 from pathlib import Path
+from typing import Any, get_args, get_type_hints
 
 from clan_cli.cmd import run_no_stdout
 from clan_cli.errors import ClanCmdError, ClanError
-from clan_cli.inventory import Inventory, load_inventory_json
+from clan_cli.inventory import Inventory, load_inventory_json, save_inventory
+from clan_cli.inventory.classes import Service
 from clan_cli.nix import nix_eval
 
 from . import API
+from .serde import from_dict
 
 
 @dataclass
@@ -153,3 +156,30 @@ def get_module_info(
 @API.register
 def get_inventory(base_path: str) -> Inventory:
     return load_inventory_json(base_path)
+
+
+@API.register
+def set_service_instance(
+    base_path: str, module_name: str, instance_name: str, config: dict[str, Any]
+) -> None:
+    service_keys = get_type_hints(Service).keys()
+
+    if module_name not in service_keys:
+        raise ValueError(
+            f"{module_name} is not a valid Service attribute. Expected one of {', '.join(service_keys)}."
+        )
+
+    inventory = load_inventory_json(base_path)
+    target_type = get_args(get_type_hints(Service)[module_name])[1]
+
+    module_instance_map: dict[str, Any] = getattr(inventory.services, module_name, {})
+
+    module_instance_map[instance_name] = from_dict(target_type, config)
+
+    setattr(inventory.services, module_name, module_instance_map)
+
+    save_inventory(
+        inventory, base_path, f"Update {module_name} instance {instance_name}"
+    )
+
+    # TODO: Add a check that rolls back the inventory if the service config is not valid or causes conflicts.