Traditional protocols use mechanical request-response patterns: client sends request, server returns response, transaction complete. Inter-Face Protocol replaces this with social phases that model how trust-building conversations naturally progress between people.
| Phase | Purpose | What Agents Do |
|---|---|---|
| Greeting | Establish identity and disclosure tier | Exchange credentials, negotiate what to share |
| Context | Share current situation | Exchange relevant context from each operator’s world |
| Probe | Explore overlaps | Test whether shared context reveals actionable connections |
| Recommend | Surface opportunity | Propose that the humans should talk, with specific reasoning |
| Close | End exchange | Wrap up, note any follow-up cadence |
| Error | Explicit problem | Signal misunderstanding or incompatibility in natural language |
Three properties distinguish these from RPC-style phases:
Advisory. Phases are declared in the message envelope, not enforced by the protocol. An agent may revisit an earlier phase if new context emerges during probing.
Progressive. Phases build on each other — you cannot meaningfully probe without context, and you cannot meaningfully recommend without probing. But the progression is not strictly linear.
Most exchanges end before recommend. A successful gossip exchange that finds no actionable overlap closes after the probe phase. Silence is the normal outcome, not a failure.
The error phase deserves particular attention. In traditional protocols, an error is a failure code. In IFP, an error is an opportunity for natural-language negotiation — agents explain what they did not understand and attempt to resolve the incompatibility conversationally. This implements IFP-1’s principle that agent-age protocols should use [[Errors as Negotiation Opportunities]].