# Claude Agent SDK
Source: https://pushary.com/docs/agents/build/claude-agent-sdk
Last updated: 2026-10-04
> Claude Agent SDK human in the loop with canUseTool. Your user taps Approve or Deny on their phone before a tool runs, and no answer means the tool is denied.
The Claude Agent SDK asks your code before it runs a tool that needs permission. It calls `canUseTool`, and whatever you return decides. `@pushary/claude-agent-sdk` adds human in the loop to the Claude Agent SDK: it is a `canUseTool` that sends the request to your user's phone and returns their answer. The tool runs only if they tap Approve.
```bash
npm i @pushary/claude-agent-sdk @anthropic-ai/claude-agent-sdk
export PUSHARY_API_KEY=pk_xxx.xxx
```
Get the key at [Partner onboarding](https://pushary.com/onboarding/partner).
## Set up Claude Agent SDK human in the loop [#set-up-claude-agent-sdk-human-in-the-loop]
### Connect a user once [#connect-a-user-once]
```ts
import { connect } from '@pushary/claude-agent-sdk'
const { universalLink } = await connect({ apiKey: process.env.PUSHARY_API_KEY! }, user.id)
```
Show `universalLink` to the signed-in user as a button or QR code. They open it on their phone once. They install the free Pushary app and never sign up or pay.
### Pass pusharyCanUseTool to query [#pass-pusharycanusetool-to-query]
```ts
import { query } from '@anthropic-ai/claude-agent-sdk'
import { pusharyCanUseTool } from '@pushary/claude-agent-sdk'
for await (const message of query({
prompt: 'Refund order 1234',
options: { canUseTool: pusharyCanUseTool({ externalId: user.id }) },
})) {
if (message.type === 'result') console.log(message.subtype)
}
```
### Run it and answer on the phone [#run-it-and-answer-on-the-phone]
When Claude wants a tool that needs permission, your user's phone buzzes with the tool name and its input. Approve runs the tool with its input unchanged.
Tools you allow with `allowedTools` never reach `canUseTool`, so your user only sees the calls that need them.
## What happens when nobody answers [#what-happens-when-nobody-answers]
The tool does not run. Each question waits up to `timeoutMs` (55 seconds by default). The model gets a denial it can read:
| Outcome | Message the model reads |
| ---------------------------------- | ----------------------------------------------------------------------------------------------- |
| Your user taps Deny | `The approver denied this action.` |
| Nobody answers in time | `No answer from the approver, so this was denied. Do not retry the same action.` |
| The run is cancelled while waiting | `The run was cancelled before anyone answered. Do not retry the same action.` |
| Pushary cannot be reached | `Pushary could not reach a person to decide, so this was denied. Do not retry the same action.` |
Cancelling the run stops the wait and denies at once.
## Who answers [#who-answers]
`externalId` is your own id for the user. Pass a string, or a function that picks the person for each call. The function also runs for `AskUserQuestion`:
```ts
pusharyCanUseTool({ externalId: (toolUse) => ownerOf(toolUse.toolName) })
```
Never take the person from the tool input. The model writes the tool input, so a prompt injection could send the approval to someone else.
## Clarifying questions from AskUserQuestion [#clarifying-questions-from-askuserquestion]
When Claude calls `AskUserQuestion`, the same `canUseTool` puts each question on the person's phone as a choice between Claude's options, with each option's description. It asks one question at a time and returns their picks as the answers. Each question waits up to `timeoutMs`.
If a question goes unanswered, Pushary takes it off the phone, denies the call and tells Claude: `Nobody answered the question in time. Do not assume an answer.` If Pushary cannot take it back within five seconds, the reason goes to `console.warn` and the question expires on its own.
The phone takes one choice per question, so a multi-select question says "(choose one)" and comes back with the one option the person picked. A question too long for the phone is denied, and Claude is told to ask it in plain text instead. Your rules are not asked about questions, including a rule that names `AskUserQuestion`, because a question is not an action.
## Site rules are off unless you turn them on [#site-rules-are-off-unless-you-turn-them-on]
Claude's tools have the same names in your own Claude Code: `Bash`, `Read`, `Write`, `WebFetch`. A rule you wrote for your own Claude Code sessions would also answer your users' calls, so by default every gated call goes to a person.
Set `policy: true` to ask your site's rules first. A rule can then allow a call without paging anyone, or deny it outright. Only turn it on for a site whose rules you wrote for this agent. Rules need a server key from Settings > API keys. With the key from onboarding, `policy: true` has no effect and every gated call still goes to a person.
## Options [#options]
| Option | What it does |
| ------------------ | ------------------------------------------------------------------------------------------------------------------ |
| `externalId` | The person who answers. Required. |
| `question` | Builds the approval text the person sees. Defaults to the tool name and its input. Not used for `AskUserQuestion`. |
| `sessionId` | Groups one session's calls, so a replayed turn does not ask twice. |
| `timeoutMs` | How long to wait for an answer before denying. Applies to each clarifying question in turn. |
| `expiresInSeconds` | How long the question stays answerable. |
| `requireReachable` | Deny at once when the person has no connected phone. |
| `policy` | Ask your site's rules before a person. Defaults to `false`. |
| `agentName` | Shown on the approval so the person knows which agent is asking. |
| `apiKey` | Defaults to `PUSHARY_API_KEY`. |
Source: [pushary-claude-agent-sdk on GitHub](https://github.com/Pushary/pushary-claude-agent-sdk). Anthropic reference: [permissions in the Agent SDK](https://code.claude.com/docs/en/agent-sdk/permissions).
## Next steps [#next-steps]