FormalClaw: Reliable Agent Communication through Verification-Grounded Protocol

Large language model agents are increasingly deployed in domains with real-world consequences, where they operate through complex reasoning processes involving tool use, environment interaction, and multi-agent coordination. This expansion creates a reliability concern beyond existing ad hoc intervention or post hoc moderation: How can agentic communication preserve precise specification without demanding end-to-end formalization? In this paper, we introduce FormalClaw, a verification-grounded communication protocol for agents. FormalClaw replaces unstructured instruction with verifier-checkable contracts that encode goals, assumptions, constraints, and evidence obligations. By making contracts and evidence as communication objects, FormalClaw generalizes formal verification from post-hoc oversight to execution-time communication. We instantiate this protocol across single-agent and multi-agent settings, and our experiments show that FormalClaw contracts can improve agent execution relative to natural-language and programmatic feedback while incurring modest verifier-side latency in our evaluations; on ClawArena, FormalClaw achieves up to a 2.16x improvement over natural-language refinement for Qwen3.5-2B. Further experiments demonstrate that FormalClaw improves robustness against vulnerability propagation and benefits iterative refinement.