Start a campaign

From a goal to a priced plan in one call: goal (launch, funding, feature or program), product, moment (what goes live and when), window_start, window_end and budget_usd; optionally audience and company (left out, they come from your company context), geography (worldwide), desired_outcome (the goal's usual outcome), constraints and budget_min_usd. The answer's defaults lists every field it filled. The budget is held to this key's mandate: the plan is built within the smaller of budget_usd, the mandate's maximum plan total and what is left of its monthly cap, and a budget_min_usd above either limit is refused (mandate_refused, over_max_plan_total or over_monthly_cap, with the numbers); with no budget_min_usd the campaign is held to the mandate instead. The campaign is started for the brand exactly as from the workspace and the planner builds the plan from creators on sale now. Returns campaign_id and the plan as plan_quote returns it, or plan_note when nothing on sale fits yet. Needs an idempotency_key; a retry with the same key never starts a second campaign. A brand starts at most 3 campaigns in any 24 hours (rate_limited, details.reason daily_campaign_limit, details.resets_at when it reopens). Scope: campaigns:write. MCP tool: create_campaign.