## What changed
Add optional JSON-encoded `parameters` to catalog tool messages and apply them to all six Multi-Agent V2 tools, including plain, namespaced, and code-mode exposure. Schema selection follows the active model, including mid-turn model changes.
Require an object schema supported by the existing `JsonSchema` subset and preserve bundled encryption annotations. Fall back to bundled parameters when overrides are missing, invalid, unsupported, or omit encrypted properties. Tool execution and argument handling remain unchanged.
## Testing
Extend integration coverage for schema overrides, fallback behavior, encryption annotations, exposure modes, and mid-turn model changes. Add a snapshot scenario exercising `list_agents` with a catalog parameter schema.
GitOrigin-RevId: 978be6d5f7e6a6865969922be5483bc697b20aca
cc7591646e