back_opinion

Spends the previewed price_coins to back the opinion. Accepts only the confirm_token from preview_back. Scope: write · Annotations: destructiveHint, idempotentHint, _meta["anthropic/requiresUserInteraction"] REST equivalent: POST /open/v1/backs

Call only after the user has reviewed the preview summary and explicitly confirmed. Tokens expire in 5 minutes and are single-use.

Parameters

Name	Type	Required	Default	Notes
`confirm_token`	string	✅	—	From `preview_back`

Returns

Captured live:

{
  "back": {
    "opinion_id": "7c2900c1-595f-4d92-bcf0-d84eba321ee2",
    "seq": 1,
    "price_coins": "1.0000",
    "backer_count": 1,
    "max_relay_payback_sapphires": "2.0000"
  },
  "replayed": false
}

The previewed price is a hard cap

Unlike place_order, this call does not fall back to the market. If other backers took the seat first and the relay price moved above what the user confirmed, the call fails with 409 OPINION_BACK_PRICE_MOVED — run preview_back again and have the user confirm the new price. Backing is once-per-person and cannot be undone, so paying more than agreed is never assumed. Retrying with the same token returns the original backing with replayed: true.

Errors

Code	HTTP	Meaning
`OPINION_BACK_PRICE_MOVED`	409	The seat’s price rose above the confirmed cap
`OPINION_ALREADY_BACKED`	409	Already backed by this user
`OPINION_BACK_FULL`	409	The price ladder is exhausted
`CONFIRM_TOKEN_EXPIRED`	409	Older than 5 minutes
`CONFIRM_TOKEN_USED`	409	Consumed by a different call
`INSUFFICIENT_BALANCE`	400	Not enough coins
`FORBIDDEN_SCOPE`	403	The key is read-only

See Errors for the full table.

Example prompts

“Yes, back it.”
“Confirmed, support that opinion.”

preview_back · list_my_backed_opinions

Getting Started

MCP Server

Platform

Parameters

Returns

The previewed price is a hard cap

Errors

Example prompts

​Parameters

​Returns

​The previewed price is a hard cap

​Errors

​Example prompts

​Related

Parameters

Returns

The previewed price is a hard cap

Errors

Example prompts

Related