Support anyOf and enum in JsonSchema by vivi · Pull Request #16875 · openai/codex

vivi · 2026-04-06T02:34:54Z

This brings us into better alignment with the JSON schema subset that is supported in [https://developers.openai.com/api/docs/guides/structured-outputs#supported-schemas], and also allows us to render richer function signatures in code mode (e.g., anyOf{null, OtherObjectType})

github-actions · 2026-04-06T02:35:08Z

All contributors have signed the CLA ✍️ ✅
_{Posted by the CLA Assistant Lite bot.}

pakrym-oai · 2026-04-06T18:56:49Z

+    }
+}
+
+fn json_schema_to_json(schema: &JsonSchema) -> JsonValue {


Why do we need custom parse/serialize methods? Can't JSON schema be represented in Rust types for default serializer/deserializer still work?

pakrym-oai · 2026-04-06T18:57:59Z

+        panic!("expected function tool");
+    };
+
+    assert!(description.contains("mcp__sample__fn(args: { open?: Array<{"));


can we use the full multiline string in contains assertion?

pakrym-oai · 2026-04-06T18:58:40Z

 }
+
+#[test]
+fn parse_tool_input_schema_preserves_web_run_shape() {


Can this test be reduced to only representative parts?

As in, specific types or patterns instead of just web_run

pakrym-oai · 2026-04-06T19:00:14Z

                    properties: BTreeMap::from([(
                        "value".to_string(),
-                        JsonSchema::String { description: None },
+                        JsonSchema::AnyOf {


Does this type anyOf definition work with response api?

yes, anyOf and Enum are supported: https://developers.openai.com/api/docs/guides/structured-outputs#supported-schemas

i will remove allOf, oneOf, and Constant though

pakrym-oai

2 major points:

Does the newly extended JSON schema format work with Responses API https://developers.openai.com/api/docs/guides/structured-outputs
Can we drop custom serializer/deserializer.

vivi · 2026-04-06T22:53:27Z

I have read the CLA Document and I hereby sign the CLA

pakrym-oai · 2026-04-07T01:36:07Z

@codex review this

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vivi · 2026-04-07T03:18:24Z

@codex review

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pakrym-oai · 2026-04-07T15:34:17Z

+}
+
+fn normalize_schema_type_name(schema_type: &str) -> Option<&'static str> {
+    match schema_type {


nit: this can be simpler

is_known_type?

pakrym-oai · 2026-04-07T15:35:52Z

+                sanitize_json_schema(value);
+            }
+
+            if let Some(const_value) = map.remove("const") {


is this new logic? do we need a test?

added parse_tool_input_schema_rewrites_const_to_single_value_enum

pakrym-oai · 2026-04-07T15:37:59Z

-                        break;
-                    }
-                }
+            if matches!(schema_type.as_deref(), Some("enum") | Some("const")) {


why would the type be enum or const? I don't think the spec supports it.

pakrym-oai · 2026-04-07T15:40:19Z

+                map.remove("type");
+            }
+
+            if let Some(types) = map.get("type").and_then(JsonValue::as_array).cloned() {


we are interchangeably using map.get("type") and schema_type around this method.

can we normalize and clean up a bit?

pakrym-oai · 2026-04-07T15:40:48Z

-                {
-                    schema_type = Some("string".to_string());
+                } else if map.contains_key("enum") || map.contains_key("format") {
+                    schema_type = infer_enum_type(map.get("enum").and_then(JsonValue::as_array))


do we need this extra logic? do we have tests?

pakrym-oai · 2026-04-07T15:44:02Z

+                map.insert("type".to_string(), JsonValue::Array(normalized));
+            }
+        }
+    } else if let Some(schema_type) = map.get("type").and_then(JsonValue::as_str)


can we always read type into the array (and turn singular type into a single item vec) for processing

That will avoid special casing multiple/singular cases everywhere.

pakrym-oai · 2026-04-07T15:45:01Z

+
+    pub fn enumeration(values: Vec<JsonValue>, description: Option<String>) -> Self {
+        Self {
+            schema_type: infer_enum_type(Some(&values)).map(JsonSchemaType::Single),


why can't the caller provide the type?

Support enum and anyOf in tool JsonSchema Trim json schema parser coverage to representative cases Simplify code mode schema rendering assertion Stabilize JsonSchema follow-up fixes Annotate JsonSchema helper call arguments Union

vivi · 2026-04-08T03:31:03Z

-                BTreeMap::from([("page".to_string(), JsonSchema::number(/*description*/ None),)]),
+                BTreeMap::from([(
+                    "page".to_string(),
+                    JsonSchema::integer(/*description*/ None),


from https://developers.openai.com/api/docs/guides/structured-outputs#supported-schemas, integer and number are both supported

Restore JsonSchema test comments Unignore passing tool schema tests Update MCP integer schema expectation Preserve defaults for nullable schema unions

pakrym-oai · 2026-04-08T04:44:32Z

            }

-            if schema_type == "array" && !map.contains_key("items") {
+            if matches!(schema_types.as_slice(), [JsonSchemaPrimitiveType::Array])


looks like this is handled in ensure_default_children_for_schema_types

pakrym-oai · 2026-04-08T04:45:55Z

    sanitize_json_schema(&mut input_schema);
-    serde_json::from_value::<JsonSchema>(input_schema)
+    let schema: JsonSchema = serde_json::from_value(input_schema)?;
+    if matches!(


nit: this is pretty specific, is it important to have the parser validate? we don't do it for other issues.

I added this specific case because the structured output supported subset of the json schema only accepts a null type when it's in a list with another valid type (previous JsonSchema didn't have null as a type so would throw a deserialization error on the {"type": "null"} case as well...)

(and as a result this existing test expects an error)

andmis requested a review from bolinfest April 6, 2026 02:40

vivi force-pushed the vivi/preserve-nested-nullable-json-schema-tool-params branch 5 times, most recently from c7c4fa6 to b01ea63 Compare April 6, 2026 03:08

etraut-openai added the oai PRs contributed by OpenAI employees label Apr 6, 2026

pakrym-oai reviewed Apr 6, 2026

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vivi force-pushed the vivi/preserve-nested-nullable-json-schema-tool-params branch from 578a2a5 to 6995d8a Compare April 6, 2026 22:41

vivi changed the title ~~Preserve nested nullable JSON-schema tool parameters in code-mode MCP rendering~~ Support anyOf and enum in JsonSchema Apr 6, 2026

github-actions bot added a commit that referenced this pull request Apr 6, 2026

@vivi has signed the CLA in #16875

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vivi force-pushed the vivi/preserve-nested-nullable-json-schema-tool-params branch from bc2f102 to d6a7b8d Compare April 6, 2026 23:58

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Comment thread codex-rs/tools/src/json_schema.rs Outdated

vivi force-pushed the vivi/preserve-nested-nullable-json-schema-tool-params branch 2 times, most recently from 9fbcb45 to fe13088 Compare April 7, 2026 03:16

vivi force-pushed the vivi/preserve-nested-nullable-json-schema-tool-params branch from fe13088 to 1bd6e39 Compare April 7, 2026 03:22

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Comment thread codex-rs/tools/src/json_schema.rs Outdated

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vivi force-pushed the vivi/preserve-nested-nullable-json-schema-tool-params branch from 1bd6e39 to a6e0b76 Compare April 8, 2026 01:32

Preserve nested nullable MCP tool schemas in code mode

df3427f

Support enum and anyOf in tool JsonSchema Trim json schema parser coverage to representative cases Simplify code mode schema rendering assertion Stabilize JsonSchema follow-up fixes Annotate JsonSchema helper call arguments Union

vivi commented Apr 8, 2026

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vivi force-pushed the vivi/preserve-nested-nullable-json-schema-tool-params branch from 1c312c4 to 1873682 Compare April 8, 2026 03:51

Simplify tool JSON schema normalization

f2f1d03

Restore JsonSchema test comments Unignore passing tool schema tests Update MCP integer schema expectation Preserve defaults for nullable schema unions

vivi force-pushed the vivi/preserve-nested-nullable-json-schema-tool-params branch from 1873682 to f2f1d03 Compare April 8, 2026 03:54

vivi added 3 commits April 7, 2026 21:00

Use direct parse_tool_input_schema import in tests

4ba00e8

Reject singleton null tool schemas

eb73f1b

Allow large tool search enum variant

7a11f4a

pakrym-oai reviewed Apr 8, 2026

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pakrym-oai approved these changes Apr 8, 2026

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Remove duplicate schema child defaults

e3b37b5

vivi merged commit ea516f9 into main Apr 8, 2026
27 of 30 checks passed

vivi deleted the vivi/preserve-nested-nullable-json-schema-tool-params branch April 8, 2026 08:07

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vivi commented Apr 6, 2026 •

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