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122 lines
4.3 KiB
Markdown
122 lines
4.3 KiB
Markdown
---
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type: agent-doc
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agent: OpenCode
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source: https://opencode.ai/docs/custom-tools/
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scraped: 2026-04-28T21:02:14.861865+00:00
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content_hash: 34c22729
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---
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# Custom Tools
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Create tools the LLM can call in opencode.
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Custom tools are functions you create that the LLM can call during conversations. They work alongside opencodeâs built-in tools like read, write, and bash.
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---
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## Creating a tool
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Tools are defined as TypeScript or JavaScript files. However, the tool definition can invoke scripts written in any language â TypeScript or JavaScript is only used for the tool definition itself.
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---
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### Location
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They can be defined:
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- Locally by placing them in the .opencode/tools/ directory of your project.
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- Or globally, by placing them in ~/.config/opencode/tools/.
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---
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### Structure
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The easiest way to create tools is using the tool() helper which provides type-safety and validation.
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```
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import { tool } from "@opencode-ai/plugin"
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export default tool({ description: "Query the project database", args: { query: tool.schema.string().describe("SQL query to execute"), }, async execute(args) { // Your database logic here return `Executed query: ${args.query}` },})
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```
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The filename becomes the tool name. The above creates a database tool.
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---
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#### Multiple tools per file
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You can also export multiple tools from a single file. Each export becomes a separate tool with the name <filename>_<exportname>:
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```
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import { tool } from "@opencode-ai/plugin"
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export const add = tool({ description: "Add two numbers", args: { a: tool.schema.number().describe("First number"), b: tool.schema.number().describe("Second number"), }, async execute(args) { return args.a + args.b },})
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export const multiply = tool({ description: "Multiply two numbers", args: { a: tool.schema.number().describe("First number"), b: tool.schema.number().describe("Second number"), }, async execute(args) { return args.a * args.b },})
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```
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This creates two tools: math_add and math_multiply.
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---
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#### Name collisions with built-in tools
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Custom tools are keyed by tool name. If a custom tool uses the same name as a built-in tool, the custom tool takes precedence.
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For example, this file replaces the built-in bash tool:
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```
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import { tool } from "@opencode-ai/plugin"
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export default tool({ description: "Restricted bash wrapper", args: { command: tool.schema.string(), }, async execute(args) { return `blocked: ${args.command}` },})
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```
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---
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### Arguments
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You can use tool.schema, which is just Zod, to define argument types.
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```
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args: { query: tool.schema.string().describe("SQL query to execute")}
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```
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You can also import Zod directly and return a plain object:
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```
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import { z } from "zod"
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export default { description: "Tool description", args: { param: z.string().describe("Parameter description"), }, async execute(args, context) { // Tool implementation return "result" },}
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```
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---
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### Context
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Tools receive context about the current session:
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```
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import { tool } from "@opencode-ai/plugin"
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export default tool({ description: "Get project information", args: {}, async execute(args, context) { // Access context information const { agent, sessionID, messageID, directory, worktree } = context return `Agent: ${agent}, Session: ${sessionID}, Message: ${messageID}, Directory: ${directory}, Worktree: ${worktree}` },})
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```
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Use context.directory for the session working directory. Use context.worktree for the git worktree root.
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---
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## Examples
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### Write a tool in Python
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You can write your tools in any language you want. Hereâs an example that adds two numbers using Python.
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First, create the tool as a Python script:
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```
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import sys
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a = int(sys.argv[1])b = int(sys.argv[2])print(a + b)
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```
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Then create the tool definition that invokes it:
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```
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import { tool } from "@opencode-ai/plugin"import path from "path"
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export default tool({ description: "Add two numbers using Python", args: { a: tool.schema.number().describe("First number"), b: tool.schema.number().describe("Second number"), }, async execute(args, context) { const script = path.join(context.worktree, ".opencode/tools/add.py") const result = await Bun.$`python3 ${script} ${args.a} ${args.b}`.text() return result.trim() },})
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```
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Here we are using the Bun.$ utility to run the Python script.
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