When the server asks for input first¶

callTool(), readResource(), and getPrompt() can answer with an InputRequiredResult instead of the result you asked for. The server needs something from the user before it can finish. Branch on the type. Do not assume the happy path.

$result = $client->callTool('book_flight', ['destination' => 'Cebu']);

if ($result instanceof InputRequiredResult) {
    // $result->inputRequests is a map of field name to InputRequest describing what to collect.
    // $result->requestState, when present, is opaque and must be echoed back verbatim.
}

Answering a tool call¶

To answer, call the tool again with the collected values and the requestState it handed you:

$answered = $client->callTool(
    name: 'book_flight',
    arguments: ['destination' => 'Cebu'],
    inputResponses: ['seat' => new ElicitResult(action: ElicitAction::Accept, content: ['seat' => '14C'])],
    requestState: $result->requestState,
);

Keep arguments the same as in the first call. The server resumes that request. It does not receive a new one. requestState must go back exactly as it arrived. It is opaque, and a server is entitled to reject a modified one.

Answering a resource read or a prompt¶

readResource() and getPrompt() answer the same way, with the same two parameters:

$contents = $client->readResource(
    uri: 'file:///report.csv',
    inputResponses: ['passphrase' => new ElicitResult(
        action: ElicitAction::Accept,
        content: ['passphrase' => 'hunter2'],
    )],
    requestState: $result->requestState,
);

$prompt = $client->getPrompt(
    name: 'walkthrough',
    arguments: ['audience' => 'a junior developer'],
    inputResponses: ['confirm_scope' => new ElicitResult(
        action: ElicitAction::Accept,
        content: ['scope' => 'full'],
    )],
    requestState: $result->requestState,
);

The same rule applies here. Repeat what the first call carried, the uri or the arguments, since the server resumes that request rather than receive a new one.