diff --git a/packages/opencode/src/session/prompt.ts b/packages/opencode/src/session/prompt.ts
index 2c799b1100f7..5e361c170d1f 100644
--- a/packages/opencode/src/session/prompt.ts
+++ b/packages/opencode/src/session/prompt.ts
@@ -1,6 +1,7 @@
 import path from "path"
 import os from "os"
 import z from "zod"
+import { zodToJsonSchema } from "zod-to-json-schema"
 import { SessionID, MessageID, PartID } from "./schema"
 import { MessageV2 } from "./message-v2"
 import { Log } from "../util/log"
@@ -436,7 +437,7 @@ NOTE: At any point in time through this workflow you should feel free to ask the
           { modelID: ModelID.make(input.model.api.id), providerID: input.model.providerID },
           input.agent,
         )) {
-          const schema = ProviderTransform.schema(input.model, z.toJSONSchema(item.parameters))
+          const schema = ProviderTransform.schema(input.model, zodToJsonSchema(item.parameters) as Record<string, unknown>)
           tools[item.id] = tool({
             id: item.id as any,
             description: item.description,