diff --git a/bmspy/classes.py b/bmspy/classes.py
index 1427c2e..8db5058 100644
--- a/bmspy/classes.py
+++ b/bmspy/classes.py
@@ -63,6 +63,7 @@ class UPS(ABC):
         ...
 
     def __bool__(self) -> bool:
+        """Return True if the UPS has at least one populated field."""
         return next(iter(self.items()), None) is not None
 
     @classmethod
diff --git a/bmspy/client.py b/bmspy/client.py
index cf0f6b9..791d749 100644
--- a/bmspy/client.py
+++ b/bmspy/client.py
@@ -15,6 +15,7 @@ is_registered = False
 
 
 def handle_registration(socket_path: str, client_name: str, debug: int = 0) -> dict[str, Any]:
+    """Register or deregister a named client with the bmspy daemon over the socket."""
     global is_registered
     data: dict[str, Any] = dict()
 
@@ -45,6 +46,7 @@ def handle_registration(socket_path: str, client_name: str, debug: int = 0) -> d
 
 
 def socket_comms(socket_path: str, request_data: dict[str, Any], debug: int = 0) -> dict[str, Any]:
+    """Send a JSON request to the daemon socket and return the decoded JSON response."""
     response_data: dict[str, Any] = dict()
 
     # Create a UDS socket
diff --git a/bmspy/influxdb.py b/bmspy/influxdb.py
index 5280a43..e537bae 100644
--- a/bmspy/influxdb.py
+++ b/bmspy/influxdb.py
@@ -12,6 +12,7 @@ DAEMON_UPDATE_PERIOD = 30
 
 
 def influx_shutdown(influxclient: InfluxDBClient3 | None) -> None:
+    """Close the InfluxDB client connection if it is not None."""
     if influxclient is not None:
         influxclient.close()
 
@@ -26,6 +27,7 @@ def influxdb_export(
     daemonize: bool = True,
     debug: int = 0,
 ) -> None:
+    """Export BMS data to InfluxDB, either once or as a daemon loop."""
     if not url:
         url = os.environ["INFLUXDB_V2_URL"]
         org = os.environ.get("INFLUXDB_V2_ORG")
@@ -48,6 +50,7 @@ def influxdb_export(
 
 
 def influxdb_write_snapshot(influxclient: InfluxDBClient3, bucket: str, ups_data: dict[str, UPS], debug: int = 0) -> None:
+    """Create InfluxDB points from ups_data and write them to the database."""
     if debug > 1:
         debugger("influxdb: creating snapshot")
     points = influxdb_create_snapshot(ups_data, debug)
diff --git a/bmspy/jbd_bms.py b/bmspy/jbd_bms.py
index 003e8a8..133e75d 100644
--- a/bmspy/jbd_bms.py
+++ b/bmspy/jbd_bms.py
@@ -52,6 +52,7 @@ class JBDBMS(UPS):
 
 
 def serial_cleanup(ser: serial.Serial, debug: int = 0) -> None:
+    """Flush and close the serial port if it is open."""
     if debug > 2:
         debugger("serial: cleaning up...")
     if ser.is_open:
@@ -79,6 +80,7 @@ def calculate_checksum(msg: bytes | bytearray) -> str:
 
 
 def verify_checksum(data: bytes | bytearray, checksum: bytes) -> bool:
+    """Verify a JBD BMS packet checksum (sum complement + 1, big-endian)."""
     # (data + length + command code) checksum, then complement, then add 1, high bit first, low bit last
     # data should have start/rw stripped
     s = 0
@@ -90,6 +92,7 @@ def verify_checksum(data: bytes | bytearray, checksum: bytes) -> bool:
 
 
 def convert_to_signed(x: int) -> int:
+    """Convert a JBD current value (possibly encoded) to a signed integer."""
     # For values below 1024, these seem to be actual results
     # For values above 1024, these seem to be encoded to account for high and negative floats
     max_uint = 1024
@@ -100,6 +103,7 @@ def convert_to_signed(x: int) -> int:
 
 
 def bytes_to_digits(high: int, low: int) -> int:
+    """Combine two bytes (high, low) into a single 16-bit unsigned integer."""
     result = high
     result <<= 8
     result = result | low
@@ -107,6 +111,7 @@ def bytes_to_digits(high: int, low: int) -> int:
 
 
 def bytes_to_date(high: int, low: int) -> str:
+    """Decode a JBD-encoded manufacture date from two bytes into 'YYYY-MM-DD' format."""
     result = bytes_to_digits(high, low)
     day = result & 0x1F
     mon = (result >> 5) & 0x0F
@@ -115,6 +120,7 @@ def bytes_to_date(high: int, low: int) -> str:
 
 
 def requestMessage(ser: serial.Serial, reqmsg: bytearray, debug: int = 0) -> bytes | str | bool:
+    """Send a request message to the BMS over serial and return the raw response bytes."""
     if debug > 2:
         debugger("serial: starting up monitor")
     if ser.is_open:
@@ -174,6 +180,7 @@ def requestMessage(ser: serial.Serial, reqmsg: bytearray, debug: int = 0) -> byt
 
 
 def parse_03_response(response: bytearray, debug: int = 0) -> JBDBMS | bool:
+    """Parse a JBD BMS 0x03 (basic info) response packet into a JBDBMS dataclass."""
     # Response is 34 bytes:
     # 00        begin:  \xDD
     # 01        r/w:    \xA5
@@ -433,6 +440,7 @@ def parse_03_response(response: bytearray, debug: int = 0) -> JBDBMS | bool:
 
 
 def parse_04_response(response: bytearray, debug: int = 0) -> BMSMultiField | bool:
+    """Parse a JBD BMS 0x04 (cell voltages) response packet into a BMSMultiField."""
     # Response is 7 + cells * 2 bytes:
     # 00        begin:  \xDD
     # 01        r/w:    \xA5
@@ -498,6 +506,7 @@ def parse_04_response(response: bytearray, debug: int = 0) -> BMSMultiField | bo
 
 
 def collect_data(ser: serial.Serial, debug: int = 0) -> JBDBMS | bool:
+    """Request both 0x03 and 0x04 packets from the BMS and return a populated JBDBMS."""
     # Request is 7 bytes:
     # \xDD for start
     # \xA5 for read, \x5A for write
diff --git a/bmspy/server.py b/bmspy/server.py
index 127e39c..d78d199 100755
--- a/bmspy/server.py
+++ b/bmspy/server.py
@@ -49,10 +49,12 @@ def signalHandler() -> NoReturn:
 
 
 def socket_cleanup(socket_path: str, debug: int = 0) -> None:
+    """Remove the Unix socket file from the filesystem."""
     os.unlink(socket_path)
 
 
 def read_request(connection: socket.socket, debug: int = 0) -> dict[str, Any]:
+    """Read a length-prefixed JSON request from a connected socket."""
     # get length of expected json string
     request = bytes()
     try:
@@ -84,6 +86,7 @@ def read_request(connection: socket.socket, debug: int = 0) -> dict[str, Any]:
 
 
 def send_response(connection: socket.socket, response_data: Any, client: str, debug: int = 0) -> None:
+    """Serialise response_data as length-prefixed JSON and send it over the socket."""
     if debug > 2:
         debugger("socket: sending {!r}".format(response_data))
     try:
diff --git a/bmspy/ups.py b/bmspy/ups.py
index 7081932..7d59976 100644
--- a/bmspy/ups.py
+++ b/bmspy/ups.py
@@ -19,6 +19,7 @@ alert_sent = False
 
 
 def handle_shutdown(action: str = "cancel", delay: int = 0, debug: int = 0) -> None:
+    """Schedule or cancel a system shutdown; only schedules once per incident."""
     global scheduled_shutdown
 
     if action == "shutdown":
@@ -42,6 +43,7 @@ def handle_email(
     mailpass: str | None = None,
     debug: int = 0,
 ) -> None:
+    """Send an alert email using SMTP, with optional STARTTLS and authentication."""
     isSSL = False
     hostname = socket.gethostname()
 
diff --git a/bmspy/utilities.py b/bmspy/utilities.py
index 4146931..1640943 100755
--- a/bmspy/utilities.py
+++ b/bmspy/utilities.py
@@ -8,6 +8,7 @@ from typing import Any
 
 
 def debugger(data: Any, pretty: bool = False) -> None:
+    """Print a timestamped debug message; use PrettyPrinter when pretty=True."""
     if pretty:
         pp = pprint.PrettyPrinter(indent=4)
         pp.pprint(