fix(schema-to-json): represent z.date() as string/date-time instead of throwing

Author: brentshulman-silkline

.changeset/schema-to-json-date-jsonschema.md

@@ -0,0 +1,5 @@
+---
+"@trigger.dev/schema-to-json": patch
+---
+
+Fix Zod 4 schema conversion throwing "Date cannot be represented in JSON Schema". `z.date()` fields now convert to `{ type: "string", format: "date-time" }` instead of aborting the whole conversion, which was causing the MCP server's `tools/list` to fail (no tools loaded) whenever a tool schema contained a date.

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

@@ -156,12 +156,19 @@ function convertZod4Schema(schema: any, options?: ConversionOptions): JSONSchema
     target: "draft-7",
     io: "output",
     reused: useReferences ? "ref" : "inline",
+    // Emit `{}` for otherwise-unrepresentable types so `override` can rewrite
+    // them, instead of Zod throwing and failing the whole conversion.
+    unrepresentable: "any",
     override: ({ zodSchema, jsonSchema }) => {
       const def = zodSchema._zod.def;
       if (def.type === "undefined") {
         throw new Error("Undefined cannot be represented in JSON Schema");
       }
 
+      if (def.type === "date") {
+        Object.assign(jsonSchema, { type: "string", format: "date-time" });
+      }
+
       if (def.type === "object" && jsonSchema.required) {
         // Early Zod 4 permalinks do not propagate optional output through unions.
         const required = jsonSchema.required.filter((key) => {

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

@@ -110,6 +110,15 @@ describe("schemaToJsonSchema", () => {
         "Undefined cannot be represented in JSON Schema"
       );
     });
+
+    it("represents dates as ISO date-time strings instead of throwing", () => {
+      const schema = z.object({ from: z.date() });
+      const result = schemaToJsonSchema(schema);
+      expect((result?.jsonSchema.properties as Record<string, unknown>).from).toMatchObject({
+        type: "string",
+        format: "date-time",
+      });
+    });
   });
 
   it("preserves explicitly required metadata on current optional schemas", () => {