Custom Tools
Custom tools are functions you create that the LLM can call during conversations. They work alongside mimocode's built-in tools like read, write, and bash.
Creating a tool
Tools are defined as TypeScript or JavaScript files. However, the tool definition can invoke scripts written in any language — TypeScript or JavaScript is only used for the tool definition itself.
Location
They can be defined:
- Locally by placing them in the
.mimocode/tools/ directory of your project.
- Or globally, by placing them in
~/.config/mimocode/tools/.
Structure
The easiest way to create tools is using the tool() helper which provides type-safety and validation.
.mimocode/tools/database.ts
1import { tool } from "@mimocode/cli/plugin"
2
3export default tool({
4 description: "Query the project database",
5 args: {
6 query: tool.schema.string().describe("SQL query to execute"),
7 },
8 async execute(args) {
9 // Your database logic here
10 return `Executed query: ${args.query}`
11 },
12})
The filename becomes the tool name. The above creates a database tool.
Multiple tools per file
You can also export multiple tools from a single file. Each export becomes a separate tool with the name <filename>_<exportname>:
.mimocode/tools/math.ts
import { tool } from "@mimocode/cli/plugin"
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
},
})
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
},
})
This creates two tools: math_add and math_multiply.
Name collisions with built-in tools
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.
For example, this file replaces the built-in bash tool:
.mimocode/tools/bash.ts
import { tool } from "@mimocode/cli/plugin"
export default tool({
description: "Restricted bash wrapper",
args: {
command: tool.schema.string(),
},
async execute(args) {
return `blocked: ${args.command}`
},
})
NOTE
Prefer unique names unless you intentionally want to replace a built-in tool. If you want to disable a built in tool but not override it, use permissions.
Arguments
You can use tool.schema, which is just Zod, to define argument types.
args: {
query: tool.schema.string().describe("SQL query to execute")
}
You can also import Zod directly and return a plain object:
1import { z } from "zod"
2
3export default {
4 description: "Tool description",
5 args: {
6 param: z.string().describe("Parameter description"),
7 },
8 async execute(args, context) {
9 // Tool implementation
10 return "result"
11 },
12}
Context
Tools receive context about the current session:
.mimocode/tools/project.ts
1import { tool } from "@mimocode/cli/plugin"
2
3export default tool({
4 description: "Get project information",
5 args: {},
6 async execute(args, context) {
7 // Access context information
8 const { agent, sessionID, messageID, directory, worktree } = context
9 return `Agent: ${agent}, Session: ${sessionID}, Message: ${messageID}, Directory: ${directory}, Worktree: ${worktree}`
10 },
11})
Use context.directory for the session working directory.
Use context.worktree for the git worktree root.
Examples
Write a tool in Python
You can write your tools in any language you want. Here's an example that adds two numbers using Python.
First, create the tool as a Python script:
.mimocode/tools/add.py
import sys
a = int(sys.argv[1])
b = int(sys.argv[2])
print(a + b)
Then create the tool definition that invokes it:
.mimocode/tools/python-add.ts
1import { tool } from "@mimocode/cli/plugin"
2import path from "path"
3
4export default tool({
5 description: "Add two numbers using Python",
6 args: {
7 a: tool.schema.number().describe("First number"),
8 b: tool.schema.number().describe("Second number"),
9 },
10 async execute(args, context) {
11 const script = path.join(context.worktree, ".mimocode/tools/add.py")
12 const result = await Bun.$`python3 ${script} ${args.a} ${args.b}`.text()
13 return result.trim()
14 },
15})
Here we are using the Bun.$ utility to run the Python script.
