# AI bot - Custom tools

**URL:** https://meta.discourse.org/t/ai-bot-custom-tools/314103
**Category:** Site Management
**Tags:** how-to, ai, ai-bot
**Created:** [June 28, 2024, 1:20am UTC](https://meta.discourse.org/t/ai-bot-custom-tools/314103 "2024-06-28T01:20:38Z")
**Posts on this page:** 1
**Showing post:** 10

<div class="post-metadata">

### Author: ![jorge-gbs](https://sea3.discourse-cdn.com/meta/user_avatar/meta.discourse.org/jorge-gbs/32/478482_2.png) [@jorge-gbs](https://meta.discourse.org/u/jorge-gbs)
#### Post date: [January 25, 2026, 3:10pm UTC](https://meta.discourse.org/t/ai-bot-custom-tools/314103/10 "2026-01-25T15:10:38Z")

</div>

I’m seeing a tool schema error when adding a custom tool with an array parameter. Error on conversation start:

```plaintext
{
“error”: {
“code”: 400,
“message”: “* GenerateContentRequest.tools[0].function_declarations[3].parameters.properties[properties].items: missing field.\n”,
“status”: “INVALID_ARGUMENT”
}
}

```

What I tried:

- Created a custom tool with a parameter named properties of type array.
- The parameter list UI doesn’t allow specifying items.
- Exported/imported a full tool JSON that includes items: { type: “string” } for properties.
- After importing, the error persists as soon as the tool is enabled for a persona. If I remove the tool, the bot works.

Expected:

Either the parameter list UI should allow defining array item types, or the import should honor items so the schema validates.

Has anyone seen this? Is there a known limitation or a required UI path for defining array params?

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