Tools (3)

Last updated Oct 20, 2026 Think provides built-in workspace file tools on every turn, plus integration points for custom tools, code execution, and dynamic extensions.

Tool merge order

On every turn, Think merges tools from multiple sources. Later sources override earlier ones if names collide:

1. Workspace tools — read, ls, find, grep, write, edit, delete, plus exec and publish when configured (built-in)
2. getTools() — your custom server-side tools
3. Extension tools — tools from loaded extensions (prefixed by extension name)
4. Session tools — set_context, load_context, search_context (from configureSession)
5. Skill tools — activate_skill, read_skill_resource, run_skill_script (from getSkills(), refer to Agent Skills)
6. MCP tools — from connected MCP servers when includeMcpTools is true
7. Client tools — from the browser (refer to Client tools)

Tools belong to the agent running the turn. For parent-child orchestration, use Agents as tools instead of passing one-off tools through chat().

Built-in workspace tools

Every Think agent gets this.workspace, a Workspace from @cloudflare/computer ↗︎ stored in the Durable Object's SQLite. Think adds Computer's AI SDK tools to every turn with no configuration.

Paths are absolute. Computer's tools and backends treat /workspace as the working root, and Think writes its own files there too.

@cloudflare/computer is a peer dependency of Think:

npm install @cloudflare/computer

Run code with exec

The default Workspace has no execution backends, so there is no exec tool until you add one. Configure the backends, and the modules they offer, on the Workspace:

import { Think } from "@cloudflare/think";
import { Workspace } from "@cloudflare/computer";
import { WorkerJavaScriptBackend } from "@cloudflare/computer/backends/worker-javascript";
import { createGitClient } from "@cloudflare/computer/git";
import { createGitModule } from "@cloudflare/computer/modules/git";

export class MyAgent extends Think {
    workspace = new Workspace({
        storage: this.ctx.storage,
        git: createGitClient(),
        backends: [
            new WorkerJavaScriptBackend({
                id: "js",
                loader: this.env.LOADER,
                access: "read-write",
                modules: { "ws:git": createGitModule() },
            }),
        ],
    });

getModel() {
        /* ... */
    }
}

import { Think } from "@cloudflare/think";
import { Workspace } from "@cloudflare/computer";
import { WorkerJavaScriptBackend } from "@cloudflare/computer/backends/worker-javascript";
import { createGitClient } from "@cloudflare/computer/git";
import { createGitModule } from "@cloudflare/computer/modules/git";

export class MyAgent extends Think<Env> {
    override workspace = new Workspace({
        storage: this.ctx.storage,
        git: createGitClient(),
        backends: [
            new WorkerJavaScriptBackend({
                id: "js",
                loader: this.env.LOADER,
                access: "read-write",
                modules: { "ws:git": createGitModule() },
            }),
        ],
    });

getModel() {
        /* ... */
    }
}

The JavaScript backend runs code in a Dynamic Worker, so it needs a Worker Loader binding:

{
  "$schema": "./node_modules/wrangler/config-schema.json",
  "worker_loaders": [
    {
      "binding": "LOADER"
    }
  ]
}

[[worker_loaders]]
binding = "LOADER"

Computer also ships a just-bash shell backend that runs in Dynamic Workers, and a container backend with a full Linux userland. Refer to the Computer README ↗︎ for each backend's bindings.

Call the agent's tools from code

Give a JavaScript backend a ws:tools module, and code the model runs with exec can import the agent's tools. Code reads files through node:fs/promises, so serve getTools() rather than the workspace tools:

import { createToolBindings } from "@cloudflare/computer/modules/tools";
import { forAISDKTools } from "@cloudflare/computer/tools/ai-sdk";

new WorkerJavaScriptBackend({
    id: "js",
    loader: this.env.LOADER,
    modules: {
        "ws:tools": createToolBindings(forAISDKTools(() => this.getTools())),
    },
});

import { createToolBindings } from "@cloudflare/computer/modules/tools";
import { forAISDKTools } from "@cloudflare/computer/tools/ai-sdk";

new WorkerJavaScriptBackend({
    id: "js",
    loader: this.env.LOADER,
    modules: {
        "ws:tools": createToolBindings(forAISDKTools(() => this.getTools())),
    },
});

Code the model runs with exec:

import { readFile } from "node:fs/promises";
import { getWeather } from "ws:tools";

export default async function () {
    const cities = JSON.parse(await readFile("/workspace/cities.json", "utf8"));
    const reports = [];
    for (const city of cities) reports.push((await getWeather({ city })).text);
    return reports;
}

ws:tools does not export tools that need approval or tools that run in the browser, because nothing can approve or run them from code. Calls from code do not go through beforeToolCall. Refer to ws:tools ↗︎ for how calls and results work.

Change the tools

exec offers every backend the Workspace has, and each backend describes itself to the model. To change a built-in tool, return a tool with the same name from getTools(). It replaces the built-in. To hide tools for a turn, return activeTools from beforeTurn.

Upgrade from @cloudflare/shell

Earlier versions of Think used a Workspace from @cloudflare/shell, which is now deprecated. Computer stores files in different tables, and Think does not move your data. To keep an existing workspace, copy its files with the script in Migrating from @cloudflare/shell to @cloudflare/computer ↗︎.

The upgrade also changes the tools:

• list is now ls.
• The in-process bash tool is gone. Add a backend to the Workspace to get exec.
• workspaceBash, createWorkspaceTools, and @cloudflare/think/tools/workspace are removed, with no replacement. To change a built-in tool, return a tool with the same name from getTools(). To hide tools for a turn, return activeTools from beforeTurn.

Refer to Upgrading to a Computer workspace ↗︎ for the full list.

Custom tools

Override getTools() to add your own tools. These are standard AI SDK tool() definitions with schemas from a library like Zod or Valibot:

import { Think } from "@cloudflare/think";
import { tool } from "ai";

import { z } from "zod";

export class MyAgent extends Think {
    getModel() {
        /* ... */
    }

getTools() {
        return {
            getWeather: tool({
                description: "Get the current weather for a city",
                inputSchema: z.object({
                    city: z.string().describe("City name"),
                }),
                execute: async ({ city }) => {
                    const res = await fetch(
                        `https://api.weather.com/v1/current?q=${city}&key=${this.env.WEATHER_KEY}`,
                    );
                    return res.json();
                },
            }),
        };
    }
}

import { Think } from "@cloudflare/think";
import { tool } from "ai";
import type { ToolSet } from "ai";
import { z } from "zod";

export class MyAgent extends Think<Env> {
    getModel() {
        /* ... */
    }

getTools(): ToolSet {
        return {
            getWeather: tool({
                description: "Get the current weather for a city",
                inputSchema: z.object({
                    city: z.string().describe("City name"),
                }),
                execute: async ({ city }) => {
                    const res = await fetch(
                        `https://api.weather.com/v1/current?q=${city}&key=${this.env.WEATHER_KEY}`,
                    );
                    return res.json();
                },
            }),
        };
    }
}

Custom tools are merged with workspace tools automatically. If a custom tool has the same name as a workspace tool, the custom tool wins.

Tool approval

Tools can require user approval before execution using the needsApproval option:

getTools(): ToolSet {
    return {
        deleteFile: tool({
            description: "Delete a file from the system",
            inputSchema: z.object({ path: z.string() }),
            needsApproval: async ({ path }) => path.startsWith("/important/"),
            execute: async ({ path }) => {
                await this.workspace.fs.rm(path);
                return { deleted: path };
            },
        }),
    };
}

When needsApproval returns true, the tool call is sent to the client for approval. The conversation pauses until the client responds with CF_AGENT_TOOL_APPROVAL.

Note

Inside the code execution tool's sandbox, needsApproval behaves differently: it maps to the Code Mode runtime's durable pause/approve/resume flow, and a function-valued needsApproval always requires approval. Refer to Approvals (human-in-the-loop).

Per-turn tool overrides

The beforeTurn hook can restrict or add tools for a specific turn:

beforeTurn(ctx: TurnContext) {
    return {
        activeTools: ["read", "write", "getWeather"],
        tools: { emergencyTool: this.createEmergencyTool() },
    };
}

activeTools limits which tools the model can call. tools adds extra tools for this turn only (merged on top of existing tools).

MCP tools

Think inherits MCP client support from the Agent base class. By default, Think converts tools from connected MCP servers to AI SDK tools and adds them to every turn.

Set waitForMcpConnections to ensure MCP servers are connected before inference runs:

export class MyAgent extends Think {
    waitForMcpConnections = true; // default 10s timeout
    // or: waitForMcpConnections = { timeout: 5000 };

getModel() {
        /* ... */
    }
}

export class MyAgent extends Think<Env> {
    waitForMcpConnections = true; // default 10s timeout
    // or: waitForMcpConnections = { timeout: 5000 };

getModel() {
        /* ... */
    }
}

If you expose MCP tools through Code Mode or another mechanism outside Think's automatic tool set, turn off direct AI SDK tool exposure:

export class MyAgent extends Think {
    includeMcpTools = false;
    waitForMcpConnections = true;

getModel() {
        /* ... */
    }
}

export class MyAgent extends Think<Env> {
    includeMcpTools = false;
    waitForMcpConnections = true;

getModel() {
        /* ... */
    }
}

includeMcpTools controls only the automatic model tool merge. MCP connections still register, restore, discover, and wait. Raw catalog access, direct calls, Code Mode connectors, and explicit this.mcp.getAITools() calls continue to work.

Use this property instead of removing MCP tool names through activeTools in beforeTurn. Think converts MCP schemas before it calls beforeTurn, so activeTools cannot avoid that conversion. To configure a connector runtime, refer to Use MCP tools with Code Mode.

Add MCP servers programmatically or via @callable methods:

import { callable } from "agents";

export class MyAgent extends Think {
    getModel() {
        /* ... */
    }

@callable()
    async addServer(name, url) {
        return await this.addMcpServer(name, url);
    }

@callable()
    async removeServer(serverId) {
        await this.removeMcpServer(serverId);
    }
}

import { callable } from "agents";

export class MyAgent extends Think<Env> {
    getModel() {
        /* ... */
    }

@callable()
    async addServer(name: string, url: string) {
        return await this.addMcpServer(name, url);
    }

@callable()
    async removeServer(serverId: string) {
        await this.removeMcpServer(serverId);
    }
}

Code execution tool

Deprecated

createExecuteTool and createExecuteRuntime are deprecated. Use exec on a JavaScript backend with a ws:tools module instead. Refer to Call the agent's tools from code. The execute tool keeps working until it is removed along with @cloudflare/codemode.

Let the LLM write and run JavaScript in a sandboxed Worker, recorded on a durable Code Mode runtime (abort-and-replay, human approvals, audit trail, reusable snippets). Requires @cloudflare/codemode and a worker_loaders binding.

npm install @cloudflare/codemode

The one-liner infers the executor from env.LOADER and a live browser (cdp.*) from env.BROWSER if bound. Pass tools for tools.*, including the workspace tools if the sandbox should reach the workspace:

import { Think } from "@cloudflare/think";
import { createAITools } from "@cloudflare/computer/tools/ai-sdk";
import { createExecuteTool } from "@cloudflare/think/tools/execute";

export class MyAgent extends Think {
    getModel() {
        /* ... */
    }

getTools() {
        return {
            execute: createExecuteTool(this, {
                tools: createAITools({ workspace: this.workspace }),
            }),
        };
    }
}

```ts import { Think } from "@cloudflare/think"; import { createAITools } from "@cloudflare/computer/tools/ai-sdk"; import { createExecuteTool } from "@cloudflare/think/tools/execute";