---
title: Custom tools
description: Create custom tools to extend opencode capabilities.
---

Custom tools are functions you create that the LLM can call during conversations. They work alongside opencode's built-in tools like `read`, `write`, and `bash`.

---

## Tool structure

The easiest way to create tools is using the `tool()` helper which provides type safety and validation:

```ts title=".opencode/tool/database.ts"
import { tool } from "@opencode-ai/plugin"

export default tool((z) => ({
  description: "Query the project database",
  args: {
    query: z.string().describe("SQL query to execute"),
  },
  async execute(args) {
    // Your database logic here
    return `Executed query: ${args.query}`
  },
}))
```

You can also import Zod directly and return a plain object:

```ts
import z from "zod/v4"

export default {
  description: "Tool description",
  args: {
    param: z.string().describe("Parameter description"),
  },
  async execute(args, context) {
    // Tool implementation
    return "result"
  },
}
```

The filename becomes the tool name. This creates a `database` tool.

---

## Arguments

Use the `z` parameter to define tool arguments with validation and descriptions:

```ts title=".opencode/tool/calculator.ts"
import { tool } from "@opencode-ai/plugin"

export default tool((z) => ({
  description: "Perform mathematical calculations",
  args: {
    expression: z.string().describe("Mathematical expression to evaluate"),
    precision: z.number().optional().describe("Decimal precision"),
  },
  async execute(args) {
    // Your calculation logic here
    return `Result: ${eval(args.expression).toFixed(args.precision || 2)}`
  },
}))
```

---

## Context

Tools receive context about the current session:

```ts title=".opencode/tool/project.ts"
import { tool } from "@opencode-ai/plugin"

export default tool((z) => ({
  description: "Get project information",
  args: {},
  async execute(args, context) {
    // Access context information
    const { project, directory, worktree } = context
    return `Project: ${project.name}, Directory: ${directory}`
  },
}))
```

---

## Tool locations

Custom tools are loaded from:

- Project: `.opencode/tool/`
- Global: `~/.config/opencode/tool/`

Files must use `.js` or `.ts` extensions.

---

## Built-in tools

opencode includes several built-in tools: `read`, `write`, `edit`, `bash`, `glob`, `grep`, `list`, `patch`, `todo`, and `task`. [Learn more](/docs/tui#tools).