Agents do not want an API key spreadsheet. They want a tool, a price, and a settle path. Syra Spend is built around that loop: the HTTP route returns 402 Payment Required until USDC settles, then the call completes.
That is x402 as product constraint, not a buzzword. Discovery lives on the live API: /.well-known/x402, OpenAPI, and GET /x402/capabilities so clients can see which networks are actually on.
What the client has to do
A machine client reads the 402 accept offers, signs payment, retries with the payment proof, and continues. Humans can use the same surface through the marketplace or the agent chat approval gate when a wallet needs an explicit pay step.
MCP wraps the same Spend tools for Cursor and Claude-style hosts. The curated profile exposes the high-value set; the full profile codegen maps the larger tool catalog. Auto-pay needs a funded payer keypair. There is no free shared sandbox on production. Self-hosted /dev exists only when you run the API yourself outside production.
Design rules I will not break
Price for machines. Fail loudly when settlement fails. Do not market unpaid 402 volume as GMV. Do not claim a network is live until capabilities say true. Keep facilitator failover boring and documented.
If your agent can discover a tool, fund a wallet, and settle a micro-call without a human procurement cycle, the rail is working. Everything else in Syra should serve that loop or get cut.