Scenario 03: Add a Custom Tool to a Plugin

User Prompt

A user wants to create an OpenCode plugin that adds a custom tool called "jira-lookup" that the AI can invoke to look up JIRA ticket details. The tool should accept a "ticket_id" argument (string) and return the ticket summary as a string.

Show how to implement this plugin with the custom tool definition, including proper schema validation.

Expected Behavior

1. Register the custom tool via the tool key in the returned hooks object — not via client.registerTool()
2. Import the tool helper from @opencode-ai/plugin
3. Define the ticket_id argument using tool.schema.string() (or a Zod equivalent) for schema validation
4. Add a .describe() call to the ticket_id schema field
5. Implement an execute function that returns a string value

Success Criteria

• Tool registered via tool key (not client.registerTool): Plugin uses tool: { 'jira-lookup': tool({...}) } in returned hooks, NOT client.registerTool()
• Imports tool helper correctly: Imports tool from @opencode-ai/plugin
• Uses tool.schema for argument validation: Uses tool.schema.string() (or Zod equivalent) for the ticket_id argument
• Schema field has .describe(): The ticket_id schema field includes a .describe() call
• Execute returns string: The execute function returns a string value

Failure Conditions

• Registers the tool using client.registerTool() instead of the tool key in the hooks object
• Imports tool from a package other than @opencode-ai/plugin
• Defines the ticket_id argument without any schema validation
• Omits .describe() from the ticket_id schema field
• The execute function returns an object or void instead of a string