docs: clarify variation_served uses variation key (dependent flags)

docs/feature-flagging/concepts/dependent-flags.md

@@ -12,17 +12,26 @@ In a flag, add a feature gate or experiment assignment. From here, you'll be abl
 
 ![Select dependent flag rule](/img/feature-flagging/dependent-flags/dependent-flag-select.png)
 
-Once a flag is selected, you're able to select the variation(s) of the flag the user is evaluated to in order to be eligible for this assignment.
+Once a flag is selected, you're able to select the parent variation(s) the user was assigned to (by variation key) in order to be eligible for this assignment.
 
-![Select the values for eligibility](/img/feature-flagging/dependent-flags/dependent-flag-value.png)
+![Select the parent variations for eligibility](/img/feature-flagging/dependent-flags/dependent-flag-value.png)
 
 Once you save, you'll see your dependent flag rule in the flag waterfall view. You can choose to make the Dependent Flag rule first so that it's evaluated first, or you can order it below other rules depending on what meets your needs.
 
 ![Flag waterfall with a Dependent Flag rule](/img/feature-flagging/dependent-flags/dependent-flag-waterfall.png)
 
 ## Configuring Dependent Flags in code
 
-Like other targeting rules, the `get_*_assignment` function must pass the relevant information to evaluate the user for the Dependent Flag rule. Specifically the dependent flag key and variation served should be passed in the function, like the following Python example:
+Like other targeting rules, the `get_*_assignment` function must pass the relevant information to evaluate the user for the Dependent Flag rule. Pass two subject attributes:
+
+- `dependent_flag` — the parent flag key (the same key you pass to `get_*_assignment` on the parent).
+- `variation_served` — the **variation key** the parent assigned, not the flag key and (for JSON flags) not the parsed JSON value.
+
+The SDK evaluates these attributes literally against the dependent-flag rule conditions. The value must match the variation key stored for the selected parent variation.
+
+### String, boolean, numeric, and integer parent flags
+
+For these flag types, the variation key and the assignment return value are the same. You can pass the parent assignment result directly:
 
 ```python
 import eppo_client
@@ -46,3 +55,36 @@ variation = client.get_string_assignment(
   "<DEFAULT-VALUE>"
 )
 ```
+
+### JSON parent flags
+
+For JSON flags, the variation **key** is the slugified variation name (for example, `Model 1` → `model-1`). The assignment function returns the **JSON value**, which is not what `variation_served` expects.
+
+Use the parent flag's `variationKey` from assignment details as `variation_served`:
+
+```python
+parent = client.get_json_assignment_details(
+  "parent-json-flag",
+  "<SUBJECT-KEY>",
+  {},
+  {},  # default JSON value
+)
+
+variation = client.get_string_assignment(
+  "<DEPENDENT-FLAG-KEY>",
+  "<SUBJECT-KEY>",
+  {
+    "dependent_flag": "parent-json-flag",
+    "variation_served": parent.evaluation_details["variationKey"],  # e.g. "exclude"
+  },
+  "<DEFAULT-VALUE>",
+)
+```
+
+:::note
+JSON variation keys are derived from the variation name at creation time (lower-cased, spaces replaced with `-`). They do not change if you rename the variation later. See [Debugging Flag Assignment](/sdks/sdk-features/debugging-flag-assignment) for the full `variationKey` / `variationValue` behavior.
+:::
+
+### Existing dependent-flag rules with a JSON parent
+
+If you created dependent-flag rules against a JSON parent flag before the Eppo UI stored variation keys correctly, re-open the rule in the flag editor and save it again so `variation_served` is stored as the variation key.