diff --git a/synapse/logging/opentracing.py b/synapse/logging/opentracing.py
index 64ef19b11692..903ec40c86f0 100644
--- a/synapse/logging/opentracing.py
+++ b/synapse/logging/opentracing.py
@@ -271,7 +271,7 @@ class _WrappedRustReporter(BaseReporter):
         def set_process(self, *args, **kwargs):
             return self._reporter.set_process(*args, **kwargs)
 
-        def report_span(self, span):
+        def report_span(self, span: "opentracing.Span") -> None:
             try:
                 return self._reporter.report_span(span)
             except Exception:
@@ -537,19 +537,19 @@ def start_active_span_follows_from(
 
 
 def start_active_span_from_edu(
-    edu_content,
-    operation_name,
-    references: Optional[list] = None,
-    tags=None,
-    start_time=None,
-    ignore_active_span=False,
-    finish_on_close=True,
-):
+    edu_content: Dict[str, Any],
+    operation_name: str,
+    references: Optional[List["opentracing.Reference"]] = None,
+    tags: Optional[Dict] = None,
+    start_time: Optional[float] = None,
+    ignore_active_span: bool = False,
+    finish_on_close: bool = True,
+) -> "opentracing.Scope":
     """
     Extracts a span context from an edu and uses it to start a new active span
 
     Args:
-        edu_content (dict): and edu_content with a `context` field whose value is
+        edu_content: an edu_content with a `context` field whose value is
         canonical json for a dict which contains opentracing information.
 
         For the other args see opentracing.tracer
@@ -603,7 +603,7 @@ def set_tag(key: str, value: Union[str, bool, int, float]) -> None:
 
 
 @ensure_active_span("log")
-def log_kv(key_values: Dict[str, Any], timestamp=None) -> None:
+def log_kv(key_values: Dict[str, Any], timestamp: Optional[float] = None) -> None:
     """Log to the active span"""
     assert opentracing.tracer.active_span is not None
     opentracing.tracer.active_span.log_kv(key_values, timestamp)
@@ -636,7 +636,9 @@ def force_tracing(span=Sentinel) -> None:
     span.set_baggage_item(SynapseBaggage.FORCE_TRACING, "1")
 
 
-def is_context_forced_tracing(span_context) -> bool:
+def is_context_forced_tracing(
+    span_context: Optional["opentracing.SpanContext"],
+) -> bool:
     """Check if sampling has been force for the given span context."""
     if span_context is None:
         return False
@@ -708,13 +710,13 @@ def inject_response_headers(response_headers: Headers) -> None:
 
 
 @ensure_active_span("get the active span context as a dict", ret={})
-def get_active_span_text_map(destination=None):
+def get_active_span_text_map(destination: Optional[str] = None) -> Dict[str, str]:
     """
     Gets a span context as a dict. This can be used instead of manually
     injecting a span into an empty carrier.
 
     Args:
-        destination (str): the name of the remote server.
+        destination: the name of the remote server.
 
     Returns:
         dict: the active span's context if opentracing is enabled, otherwise empty.
@@ -733,7 +735,7 @@ def get_active_span_text_map(destination=None):
 
 
 @ensure_active_span("get the span context as a string.", ret={})
-def active_span_context_as_string():
+def active_span_context_as_string() -> str:
     """
     Returns:
         The active span context encoded as a string.