1
Select accounts
Pick one or more linked accounts from the dropdown.
2
Configure actions (optional)
Expand Actions to enable or disable specific actions. Selection locks once the conversation starts.
3
Chat
Try a prompt like the ones below — each tool call and its response appear in the chat log.
Model selection
Click the model selector at the bottom right to switch models:StackOne Tool Calling Model (Beta)StackOne is fine-tuning a specialized model optimized for SaaS tool calling, at lower cost than leading models. Contact ai@stackone.com to join the beta.
Defender
The configuration sidebar has a StackOne Defender toggle that scans tool call responses for prompt injection before the model sees them. It’s a per-request override: it applies to the Playground session only, whatever your project-level setting is, and defaults to on. Use it to see how your agent behaves with Defender on or off without changing your project configuration. With Defender enabled, every tool call in the chat log carries a risk icon next to its status badge:| Icon | Meaning |
|---|---|
 | Low risk — response passed Defender’s checks |
 | Medium risk — flagged but not blocked |
 | High or critical risk — blocked from reaching the model when Block High Risk Content is on in Defender |
| no icon | Defender did not scan this response (toggle off, size limit exceeded, or no Defender metadata) |
Blocked status in the chat log and the model receives an error in place of the tool response, which the agent can retry, skip, or surface like any other tool error.
Defender
Detection modes, thresholds, large-response behavior, and SDK overrides.
Common errors
No accounts visible
No accounts visible
Check the account is linked on the Accounts page, and that actions are enabled on its connector profile.
Slow responses
Slow responses
Switch to Claude Haiku (the fastest option) or reduce the number of selected accounts.
Tool not found
Tool not found
Verify the action is enabled on the connector profile, then check Request Logs for the failing call.
Connect your own client
The Use Setup button shows the MCP config for your accounts (endpoint, authentication header,x-account-id) so you can move from testing to your own agent. See MCP.