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boost::taar::jsonrpc::request_scope — Per-request state a JSON-RPC method or MCP tool can ask for by declaring a request_scope const& (or std::shared_ptr<request_scope>) parameter.
// In header: <boost/taar/jsonrpc/request_scope.hpp>
class request_scope : public std::enable_shared_from_this< request_scope > {
public:
// public member functions
request_scope(boost::json::value, boost::asio::any_io_executor);
boost::json::value const & id() const noexcept;
boost::asio::cancellation_slot slot();
bool cancelled() const noexcept;
void cancel(boost::asio::cancellation_type = boost::asio::cancellation_type::all);
void send_notification(std::string_view, boost::json::value = {}) const;
void report_progress(double, std::optional< double > = std::nullopt,
std::string = {}) const;
// public data members
std::optional< boost::json::value > progress_token; // MCP _meta.progressToken of the request, when the client sent one.
std::function< void(boost::json::value)> notify; // Where notifications go (set by the endpoint); empty on transports without a stream.
};It carries the request id, a cancellation slot that the endpoint fires when the request is cancelled (asynchronous operations the callable awaits are interrupted; a synchronous callable can poll cancelled), and a sink for server-to-client notifications such as MCP progress.
mcp.tool("export", "Long running", [](jsonrpc::request_scope const& scope, int items) -> taar::awaitable<std::string> { for (int i = 0; i < items && !scope.cancelled(); ++i) { co_await do_one(i); scope.report_progress(i + 1, items); } co_return "done"; }, mcp_arg("items"));
request_scope public member functionsrequest_scope(boost::json::value id, boost::asio::any_io_executor executor);
boost::json::value const & id() const noexcept;The request's
id (null for notifications). boost::asio::cancellation_slot slot();The slot the endpoint binds to the method's coroutine.
Not for callables: the coroutine's own cancellation state already interrupts every co_await inside it when the request is cancelled, and assigning this slot would replace that binding.
bool cancelled() const noexcept;True once cancel was called.
void cancel(boost::asio::cancellation_type type = boost::asio::cancellation_type::all);Cancel the request: marks it and emits the signal on the request's executor.
void send_notification(std::string_view method, boost::json::value params = {}) const;Send a JSON-RPC notification to the client, if the transport supports it.
void report_progress(double progress, std::optional< double > total = std::nullopt, std::string message = {}) const;Send an MCP
notifications/progress for this request. No-op when the client sent no progressToken or the transport has no stream.