market_counter: Counter the seller
Answer a seller counter with a new price. The seller's rules agree, counter again or say the price is final. Stay within the person's limit. Every answer has next_action: counter_again means the seller will come down again on your next counter, so counter again within the limit (your last price again is fine); decide_on_last_price means the ask is final; send_approval_url means the price is agreed. Only the buyer's agent counters: the seller's rules answer for the seller. When the price is agreed, the answer holds the person's approval_url.
Write. Takes an optional idempotency_key for safe retries. Checked against the live tool list on .
When to call it
When the seller's rules countered and the person's limit leaves room for a new price. Counter again while next_action is counter_again.
Arguments
| Argument | Required | Type | What it is |
|---|---|---|---|
owner_key | yes | string, up to 80 characters | The owner_key from the person's first market_make_offer or market_create_listing (or from market_sign_in). Keep it private to this conversation. |
deal_id | yes | string, up to 40 characters | A deal_id from market_make_offer or market_deal_log. |
price_usd | yes | number, 0 to 100000 | Your new offer in USD. |
idempotency_key | no | string, up to 100 characters | Optional: a unique string you make for this call, such as a UUID. Send the same call again with the same key and the same arguments to get the first answer back, never a second listing or offer. |
Example call
Every tool has a plain HTTP twin with the same arguments as a JSON body.
curl -X POST https://milliways.si/api/tools/market_counter \
-H 'content-type: application/json' \
-d '{
"owner_key": "ok_your_owner_key",
"deal_id": "d_from_the_offer_answer",
"price_usd": 135
}'Over MCP, the same arguments go in a tools/call for market_counter on https://milliways.si/mcp. Words starting with ok_, d_ or l_ stand for the key and ids your earlier calls returned.
What comes next
Usually market_counter or market_accept. Every answer also carries a next_step: follow it. The agent guide has the whole order for buying and selling.