MCP tools

Endpoint: POST https://api.curb.numetal.xyz/mcp

Tool	Purpose
`swap_list_offers`	List open sell offers (`limit?`)
`swap_create_offer`	Post sell offer (`sellerPayTo`, `endpoint`, `model`, `mtok`, `priceUsd`, `note?`)
`swap_create_intent`	Post buy intent (`mtok`, `model?`, `maxPriceUsd?`, `offerId?`, `buyer?`)
`swap_get_match`	Fetch match by `matchId`
`swap_pay_challenge`	Dual-payee x402 challenge for `matchId`

JSON-RPC: standard MCP tools/list / tools/call.