Tools
Zod ships a fully functional client-side function-calling toolbelt. The model can call built-in tools, custom JavaScript tools you write, and MCP server tools — all executed in your browser, with results fed back into the conversation.
The tool loop
When you send a message, Zod calls your provider with all tool schemas. If the model requests tool calls, Zod executes them in the browser and appends the results, repeating up to 6 rounds before streaming the final answer. Tools are dispatched through a shared runAnyTool in this order: custom → MCP → built-in — so custom and MCP tools work identically in chat, the scheduler, and agent steps.
Built-in tools
Nine tools ship with Zod. Each declares a JSON Schema and a runner, wired together so the model always gets accurate call signatures.
| Tool | Actions | What it does |
|---|---|---|
| memory | read / write / delete / clear | Long-term markdown memory blocks (## heading), persists across sessions |
| todo | add / check / uncheck / delete / list | Persistent to-do list, persisted as markdown |
| calculator | evaluate | Safe arithmetic with a hand-written tokenizer/parser: + - * / % ^, parentheses, sqrt, exp, log/ln, trig, min/max, pi, e |
| clipboard | read / write | System clipboard access (requires browser permission) |
| timer | set / list / cancel | In-browser reminders that surface as a chat message + browser Notification |
| code_tools | json_format / json_validate / yaml_to_json / json_to_yaml / yaml_format | JSON & YAML utilities, including the global-aligned YAML formatter |
| confirm | ask | Prompts the user with a yes/no modal before destructive actions |
| random | uuid / dice / number / hash | UUIDs, dice rolls, random numbers, WebCrypto hashes |
| time | now / convert / list_timezones | Current time, timezone conversions, common IANA zones |
Custom tools
Define your own tools in Settings → Tools as YAML with a JavaScript implementation. When the model calls one, the code runs in a sandbox exposing sandbox.args (the tool arguments) and sandbox.ctx (persistent state, fetch, timers, askUser, and memory getters/setters) and returns a string or JSON value back into the loop.
tools:
- name : greet
description : Greet a person by name
implementation: |
export default ({ args, ctx }) => {
return `Hello, ${args.name}!`;
};How tool context persists
Tool execution wires persistent state into every call: memory and todos are handed to the tools, changes are saved after every mutation, and the timer registry and the askUser bridge are provided. That state lives in the same localStorage document as everything else, so tools remember across sessions.
Memory
Markdown blocks persisted across sessions
Todos
Persistent to-do list