[Feat]: Multi-Attribute Negotiation and Coordination Protocol for AP2

[eunujwal]

Is your feature request related to a problem? Please describe.

Right now, AP2 handles payment authorization beautifully, but it's missing a huge piece of the puzzle - agents can't actually negotiate like humans do.
When I buy a flight, I'm not just looking at price. I'm weighing departure times, layovers, seat selection, baggage fees, cancellation policies, and maybe even carbon offsets. But current agent systems basically just sort by price and call it a day. That's not how real purchasing decisions work.

The bigger problem hits when you have multiple agents trying to coordinate. Say I want my agent to book a business trip - it needs to talk to airline agents, hotel agents, and ground transport agents, all while respecting my preferences for schedule, budget, and comfort. Right now, there's no standard way for these agents to negotiate packages or handle the inevitable conflicts ("the only flight that works arrives after hotel check-in closes").

Describe the solution you'd like

I'd like to see AP2 v2 include a negotiation protocol layer that sits between intent capture and payment execution. Something like:

Multi-attribute negotiation fields in the Cart Mandate - not just price, but delivery windows, service levels, warranty terms, bundle options.

Standardized negotiation messages that agents can exchange - "I can accept this price if delivery is by Tuesday" or "I'll take 3 units if you can do 10% off"

Smart contract templates for common scenarios (subscription services, bulk orders, service agreements) that agents can populate and execute

Built-in escrow and milestone tracking so complex transactions don't fall apart halfway through

Dispute resolution protocol with clear escalation paths - agent-to-agent resolution first, then automated arbitration, then human intervention

The key is making this composable - start with simple price/quantity negotiations, but build it so developers can add custom negotiation dimensions for their specific domains.

Describe alternatives you've considered

Building negotiation on top of AP2 - Each platform creates its own negotiation protocol and just uses AP2 for final payment. But then we're back to fragmentation hell, with every marketplace doing things differently.

Extending existing protocols - Could try adapting FIPA Contract Net or other academic agent negotiation protocols. But they're not designed for commercial transactions and don't integrate with payment systems.

Waiting for A2A to handle it - Google's Agent-to-Agent protocol might eventually cover this, but it's focused on general communication, not commerce-specific negotiation with legal/financial implications.

Manual approval workflows - Keep requiring human approval for complex negotiations. But that defeats the whole point of autonomous agents.

Additional context

No response

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