Tools API - Smithers

A tool is an AI SDK tool an agent may call. defineTool wraps one with Smithers runtime context: a deterministic idempotency key, side-effect metadata, and the side-effect snapshot hook. The five built-in tools (read, write, edit, grep, bash) are themselves defineTool results and run inside the task’s sandbox.

import {
  defineTool,
  getDefinedToolMetadata,
  bash,
  read,
  write,
  edit,
  grep,
  tools,
} from "smithers-orchestrator";

defineTool

Wrap a Zod-validated execute function into a durable AI SDK tool. Pass the result to an agent’s tools or a <Task>’s tools prop.

function defineTool<S extends ZodType>(options: DefineToolOptions<S>): Tool;

name

string

required

Tool name surfaced to the agent and stamped onto ctx.toolName. Also the default description.

description

string

Human-readable description the agent sees. Defaults to name.

schema

ZodType

required

Zod schema for the tool’s input. Validated by the AI SDK before execute runs; execute receives the parsed args.

sideEffect

boolean

default:"false"

Marks the tool as mutating external state. Opts the tool into Smithers side-effect tracking and runs the durability snapshot hook after execute.

idempotent

boolean

default:"!sideEffect"

Whether re-running with the same input is safe. Defaults to true when sideEffect is false. With sideEffect: true, idempotent: false, retries inject a warning that the tool was already called so the agent can verify external state first.

execute

(args, ctx) => Promise<unknown>

required

Runs the tool. args is the parsed input; ctx is the tool context. If sideEffect: true, idempotent: false and execute omits the second ctx parameter, Smithers logs a startup warning, since you almost certainly need ctx.idempotencyKey to handle retries safely.

Show ctx: ToolContext

ctx.idempotencyKey

string

Deterministic for a given task + iteration; stable across retries and resumes. Pass it to external APIs that support idempotency (Stripe, AWS) to deduplicate.

ctx.toolName

string

The tool’s name.

ctx.sideEffect

boolean

Resolved sideEffect flag.

ctx.idempotent

boolean

Resolved idempotent flag.

ctx.runId

string

Current run id (RUN_ID).

ctx.nodeId

string

Task node that invoked the tool (NODE_ID).

ctx.iteration

number

Loop iteration index.

ctx.attempt

number

Retry attempt number.

ctx.seq

number

Task-local tool-call sequence counter.

ctx.rootDir

string

default:"process.cwd()"

Sandbox root. Paths resolve against it; escapes are rejected.

ctx.allowNetwork

boolean

default:"false"

Whether network commands are permitted (used by bash).

ctx.maxOutputBytes

number

default:"200000"

Output truncation / size limit (200KB).

ctx.timeoutMs

number

default:"60000"

Process timeout for bash and grep (60s).

ctx.durabilitySnapshot

(name, toolUseId) => Promise<unknown>

Side-effect snapshot hook. No-op unless the engine supplies a real handle; snapshot failures never fail the tool.

Tool

object

An AI SDK tool with attached Smithers metadata. Read the metadata with getDefinedToolMetadata.

import { defineTool } from "smithers-orchestrator";
import { z } from "zod";

const placeOrder = defineTool({
  name: "wholefoods.place_order",
  description: "Place a grocery order",
  schema: z.object({ sku: z.string() }),
  sideEffect: true,
  idempotent: false,
  async execute(args, ctx) {
    return wholeFoods.placeOrder({
      sku: args.sku,
      idempotencyKey: ctx.idempotencyKey,
    });
  },
});

The sideEffect / idempotent pair drives retry behavior:

`sideEffect`	`idempotent`	Behavior
`false`	`true`	Pure read. Replayed freely. No warnings.
`true`	`true`	Mutates, but replay-safe (e.g. an upsert or PUT). No warnings.
`true`	`false`	Mutates and not replay-safe (e.g. send email, charge payment). Retry warns the agent and supplies a stable `ctx.idempotencyKey`.

The rule: if you cannot undo it with git reset, mark it sideEffect: true. Source defineTool.js · context.js · Tests tools-unit.test.js, define-tool-durability.test.js · See also Built-in Tools, SDK agents

getDefinedToolMetadata

Read the Smithers metadata attached by defineTool. Returns null for plain AI SDK tools or non-objects.

function getDefinedToolMetadata(value: unknown):
  | { name: string; sideEffect: boolean; idempotent: boolean }
  | null;

value

unknown

required

A tool (or any value). Inspected for the Symbol.for("smithers.tool.metadata") property.

metadata

object | null

Show metadata

name

string

The tool’s name.

sideEffect

boolean

Resolved side-effect flag.

idempotent

boolean

Resolved idempotency flag.

import { getDefinedToolMetadata, write } from "smithers-orchestrator";

getDefinedToolMetadata(write);
// { name: "write", sideEffect: true, idempotent: false }

Source defineTool.js · Tests tools-unit.test.js · See also defineTool

Built-in tools

Five defineTool results, all sandboxed to ctx.rootDir (the workflow directory by default). Paths resolve against the root; symlink escapes are rejected. Output is truncated to ctx.maxOutputBytes (200KB). Import them individually or as the tools bundle:

import { tools } from "smithers-orchestrator";
// tools === { read, write, edit, bash, grep }
const { read, write, edit, bash, grep } = tools;

Tool	`sideEffect`	`idempotent`
`read`	`false`	`true`
`grep`	`false`	`true`
`write`	`true`	`false`
`edit`	`true`	`false`
`bash`	`true`	`false`

read

Read a UTF-8 file from the sandbox.

path

string

required

File path, relative to rootDir or absolute within it.

Returns the file contents. Throws if the file exceeds maxOutputBytes.

write

Write content to a file, creating parent directories as needed.

path

string

required

Destination path, relative to rootDir or absolute within it.

content

string

required

File contents.

Returns "ok". Throws TOOL_CONTENT_TOO_LARGE if content exceeds maxOutputBytes; only the content’s byte size and SHA-256 hash are logged, never the content itself.

edit

Apply a unified-diff patch to an existing file.

path

string

required

File to patch. Must already exist.

patch

string

required

A unified diff. Applied against the current contents.

Returns "ok". Throws TOOL_PATCH_TOO_LARGE (patch over maxOutputBytes) or TOOL_PATCH_FAILED (the patch context does not match the file).

grep

Search for a pattern with ripgrep (rg -n). Requires rg on PATH.

pattern

string

required

Regex to search for.

path

string

default:"."

Directory or file to search, relative to rootDir.

Returns matching lines as file:line:text. No matches returns an empty string; an rg error (exit code 2) throws TOOL_GREP_FAILED.

bash

Run an executable with arguments. There is no shell parsing: pass arguments via args, and for pipes or redirects invoke a shell explicitly, e.g. { cmd: "sh", args: ["-lc", "..."] }.

cmd

string

required

Executable name or path. Up to 8,192 characters.

args

string[]

Arguments. Up to 128 entries, each up to 8,192 characters.

opts

{ cwd?: string }

cwd sets the working directory (sandboxed under rootDir). Defaults to rootDir.

Returns combined stdout and stderr, truncated to maxOutputBytes. A non-zero exit code throws TOOL_COMMAND_FAILED. The process is killed with SIGKILL after ctx.timeoutMs (default 60s; the hard cap is one hour).

Network is blocked unless allowNetwork is enabled (via RunOptions, --allow-network, or server config). When blocked, Smithers rejects commands whose executable basename is curl, wget, npm, bun, or pip, any token beginning with http:// or https://, and git together with a push, pull, fetch, clone, or remote token (throwing TOOL_NETWORK_DISABLED or TOOL_GIT_REMOTE_DISABLED). Local git commands such as git status are allowed. On macOS, a blocked bash additionally runs under sandbox-exec with a network-deny profile when available.

import { ToolLoopAgent as Agent } from "ai";
import { anthropic } from "@ai-sdk/anthropic";
import { createSmithers, tools, Task } from "smithers-orchestrator";
import { z } from "zod";

const codeAgent = new Agent({
  model: anthropic("claude-fable-5"),
  tools, // { read, write, edit, bash, grep }
});

const { Workflow, smithers, outputs } = createSmithers({
  result: z.object({ summary: z.string() }),
});

export default smithers((ctx) => (
  <Workflow name="refactor">
    <Task id="refactor" output={outputs.result} agent={codeAgent}>
      {`Refactor ${ctx.input.file} for readability and run the tests.`}
    </Task>
  </Workflow>
));

Source tools/index.js · bash.js, read.js, write.js, edit.js, grep.js · Tests tools-unit.test.js · See also Built-in Tools, Common External Tools, SDK agents

​defineTool

​getDefinedToolMetadata

​Built-in tools

​read

​write

​edit

​grep

​bash

defineTool

getDefinedToolMetadata

Built-in tools

read

write

edit

grep

bash