order check HOW

order_check — How it works¶

📌 Overview¶

This example shows how to use the low-level method order_check() to verify trade request executability before actually sending it to the server.

The method is used at the pre-trade validation stage and answers a key question:

"Will the server accept such a trade right now under current conditions?"

Important: order_check() does not open a trade and does not change account state. It is used exclusively for verification.

Method Signature¶

async def order_check(
    request: OrderCheckRequest,
    deadline: Optional[datetime] = None,
    cancellation_event: Optional[asyncio.Event] = None,
) -> OrderCheckData

Key points:

the method is asynchronous
accepts an almost complete trade request
performs server-side validation
does not create an order and does not reserve funds

🧩 Code Example — Checking multiple volumes¶

async def check_multiple_volumes():
    volumes = [0.01, 0.05, 0.10, 0.50, 1.00]

    print("Checking volumes for EURUSD BUY:")
    print("-" * 60)

    for volume in volumes:
        request = OrderCheckRequest()
        request.mql_trade_request.action = TRADE_ACTION_DEAL
        request.mql_trade_request.symbol = "EURUSD"
        request.mql_trade_request.volume = volume
        request.mql_trade_request.order_type = ORDER_TYPE_TF_BUY
        request.mql_trade_request.price = 0.0
        request.mql_trade_request.deviation = 20
        request.mql_trade_request.type_filling = ORDER_FILLING_FOK
        request.mql_trade_request.type_time = ORDER_TIME_GTC

        result = await account.order_check(request)

        if result.mql_trade_check_result.returned_code == 0:
            print(
                f"[OK] {volume:>6.2f} lots - "
                f"Margin: ${result.mql_trade_check_result.margin:>10,.2f}, "
                f"Free: ${result.mql_trade_check_result.free_margin:>10,.2f}"
            )
        else:
            print(
                f"[FAIL] {volume:>6.2f} lots - "
                f"{result.mql_trade_check_result.comment}"
            )

🟢 Detailed Explanation¶

1️⃣ Iterating Through Potential Volumes¶

volumes = [0.01, 0.05, 0.10, 0.50, 1.00]

Here user code:

defines possible position sizes
does not know in advance which are acceptable
uses order_check() as a verification tool

2️⃣ Forming Trade Request¶

request.mql_trade_request.action = TRADE_ACTION_DEAL
request.mql_trade_request.symbol = "EURUSD"
request.mql_trade_request.volume = volume
request.mql_trade_request.order_type = ORDER_TYPE_TF_BUY

Important:

the request structure matches a real order
all critically important parameters are set
this is a planned, not an actual trade

3️⃣ Server-Side Order Validation¶

result = await account.order_check(request)

At this stage the server checks:

parameter correctness
fund sufficiency
broker trading restrictions
current market conditions
execution possibility (filling, deviation)

No account state changes occur.

4️⃣ Analyzing Validation Result¶

result.mql_trade_check_result.returned_code

Interpretation:

0 — order can be executed
non-zero value — order will be rejected

Additionally returned:

calculated margin
free margin after the trade
text comment explaining rejection reason

5️⃣ Identifying Acceptable Volume Range¶

By iterating through volumes, user code:

finds the maximum acceptable volume
sees where rejection begins
gets the exact reason for the limitation

This is the final stage before actual trading.

The Role of Low-Level Method¶

Clear boundary of responsibility:

order_check():

validates trade request on the server
returns technical validation result
does not make trading decisions

User code:

forms trade parameters
iterates through volumes
interprets the result
decides whether to send the order

Summary¶

This example illustrates the last safe step before trading:

check executability → analyze result → make decision

The order_check() method is designed for strict pre-trade validation and should be used before order_send(), especially when dynamically selecting volume and in automated trading.