diff --git a/src/schema/README.md b/src/schema/README.md
index 44e8d78bc0..6d2225bf69 100644
--- a/src/schema/README.md
+++ b/src/schema/README.md
@@ -261,9 +261,9 @@ The following functions should be defined by an interpreter:
 
 | Function                                        | Definition                                                                                                                                | Example                                                | Note                                                                           |
 | ----------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------ | ------------------------------------------------------------------------------ |
-| `count(arg: array, val: any)`                   | Number of elements in an array equal to `val`                                                                                             | `count(columns.type, "EEG")`                           | The number of times "EEG" appears in the column "type" of the current TSV file |
+| `count(arg: array, val: any) -> int`            | Number of elements in an array equal to `val`                                                                                             | `count(columns.type, "EEG")`                           | The number of times "EEG" appears in the column "type" of the current TSV file |
 | `exists(arg: str \| array, rule: str) -> int`   | Count of files in an array that exist in the dataset. String is array with length 1. See following section for the meanings of rules.     | `exists(sidecar.IntendedFor, "subject")`               | True if all files in `IntendedFor` exist, relative to the subject directory.   |
-| `index(arg: array, val: any)`                   | Index of first element in an array equal to `val`, `null` if not found                                                                    | `index(["i", "j", "k"], axis)`                         | The number, from 0-2 corresponding to the string `axis`                        |
+| `index(arg: array, val: any) -> int`            | Index of first element in an array equal to `val`, `null` if not found                                                                    | `index(["i", "j", "k"], axis)`                         | The number, from 0-2 corresponding to the string `axis`                        |
 | `intersects(a: array, b: array) -> bool`        | `true` if arguments contain any shared elements                                                                                           | `intersects(dataset.modalities, ["pet", "mri"])`       | True if either PET or MRI data is found in dataset                             |
 | `allequal(a: array, b: array) -> bool`          | `true` if arrays have the same length and paired elements are equal                                                                       | `intersects(dataset.modalities, ["pet", "mri"])`       | True if either PET or MRI data is found in dataset                             |
 | `length(arg: array) -> int`                     | Number of elements in an array                                                                                                            | `length(columns.onset) > 0`                            | True if there is at least one value in the onset column                        |