fix(schema-to-json): handle Zod 4 dates when converting to JSON Schema

Author: MauryaQbit

.changeset/tidy-dates-shout.md

@@ -0,0 +1,5 @@
+---
+"@trigger.dev/schema-to-json": patch
+---
+
+Fixed MCP `tools/list` failing with "Date cannot be represented in JSON Schema" when a tool used `z.date()`. Date fields now show up as date-time strings instead of breaking the whole tool list.

packages/schema-to-json/src/index.ts

@@ -156,8 +156,17 @@ function convertZod4Schema(schema: any, options?: ConversionOptions): JSONSchema
     target: "draft-7",
     io: "output",
     reused: useReferences ? "ref" : "inline",
+    // Dates (and other unrepresentable types) throw by default, which fails the
+    // whole conversion. Fall back to `any` and handle dates in override instead.
+    unrepresentable: "any",
     override: ({ zodSchema, jsonSchema }) => {
       const def = zodSchema._zod.def;
+      if (def.type === "date") {
+        jsonSchema.type = "string";
+        jsonSchema.format = "date-time";
+        return;
+      }
+
       if (def.type === "undefined") {
         throw new Error("Undefined cannot be represented in JSON Schema");
       }

packages/schema-to-json/tests/index.test.ts

@@ -52,6 +52,23 @@ describe("schemaToJsonSchema", () => {
       });
     });
 
+    it("should convert a Zod 4 object schema with a date field", () => {
+      const schema = z4.object({
+        when: z4.date(),
+      });
+
+      const result = schemaToJsonSchema(schema);
+
+      expect(result).toBeDefined();
+      expect(result?.jsonSchema).toMatchObject({
+        type: "object",
+        properties: {
+          when: { type: "string", format: "date-time" },
+        },
+        required: ["when"],
+      });
+    });
+
     it("should convert a Zod schema with optional fields", () => {
       const schema = z3.object({
         id: z3.string(),