diff --git a/server/webserver.py b/server/webserver.py
index 738b300..8fe1ff5 100644
--- a/server/webserver.py
+++ b/server/webserver.py
@@ -165,8 +165,14 @@ class WebServer:
                     sources = query.get(k).split(",")
                     spots = [s for s in spots if s.source and s.source in sources]
                 case "sig":
+                    # If a list of sigs is provided, the spot must have a sig and it must match one of them
                     sigs = query.get(k).split(",")
                     spots = [s for s in spots if s.sig and s.sig in sigs]
+                case "needs_sig":
+                    # If true, a sig is required, regardless of what it is, it just can't be missing.
+                    needs_sig = query.get(k).upper() == "TRUE"
+                    if needs_sig:
+                        spots = [s for s in spots if s.sig]
                 case "band":
                     bands = query.get(k).split(",")
                     spots = [s for s in spots if s.band and s.band in bands]
diff --git a/webassets/apidocs/openapi.yml b/webassets/apidocs/openapi.yml
index cf74237..104bbf2 100644
--- a/webassets/apidocs/openapi.yml
+++ b/webassets/apidocs/openapi.yml
@@ -65,7 +65,7 @@ paths:
               - APRS-IS
         - name: sig
           in: query
-          description: "Limit the spots to only ones from one or more Special Interest Groups. To select more than one SIG, supply a comma-separated list."
+          description: "Limit the spots to only ones from one or more Special Interest Groups provided as an argument. To select more than one SIG, supply a comma-separated list."
           required: false
           schema:
             type: string
@@ -83,6 +83,13 @@ paths:
               - ILLW
               - ZLOTA
               - IOTA
+        - name: needs_sig
+          in: query
+          description: "Limit the spots to only ones from a Special Interest Grous such as POTA. Because supplying all known SIGs as a `sigs` parameter is unwieldy, and leaving `sigs` blank will also return spots with *no* SIG, this parameter can be set true to return only spots with a SIG, regardless of what it is, so long as it's not blank. This is what Field Spotter uses to exclude generic cluster spots and only retrieve xOTA things."
+          required: false
+          schema:
+            type: boolean
+            default: false
         - name: band
           in: query
           description: "Limit the spots to only ones from one or more bands. To select more than one band, supply a comma-separated list."