Before MCP, before A2A, there was FIPA-ACL. In 2000 the IEEE Foundation for Intelligent Physical Agents ratified an agent communication language with twenty performatives, two content languages, and a set of interaction protocols — contract net, subscribe/notify, request-when. It faded from industry because the ontology overhead was too heavy for the web, but the LLM revival of multi-agent systems is quietly reimplementing the same ideas without the formal semantics: JSON contracts stand in for performatives, natural language stands in for ontologies. This lesson reads FIPA-ACL seriously so you can see which 2026 protocol decisions are reinvention, which are novelty, and where the current wave is going to rediscover problems the 2000s already solved.
The 2026 agent-protocol landscape is busy: MCP for tools, A2A for agents, ACP for enterprise audit, ANP for decentralized trust, NLIP for natural-language content, plus CA-MCP and two dozen research proposals. Each spec announces itself as foundational.
The honest read is that most of them are rediscovering a very specific twenty-year-old decision tree. Speech-act theory from Austin (1962) and Searle (1969) gave us "utterances are actions." KQML (1993) turned that into a wire protocol. FIPA-ACL (ratified 2000) produced the reference standardization: twenty performatives, content languages SL0/SL1, interaction protocols for contract-net and subscribe-notify. JADE and JACK were the Java reference platforms. The effort faded around 2010 because the ontology overhead was too heavy and the web was winning.
When you look at MCP's tools/call, A2A's task lifecycle, or CA-MCP's shared context store, you are looking at a softer, JSON-native rehash of FIPA decisions. Knowing the heritage tells you two things: which new "innovations" are actually reinventions, and which old failure modes the new specs will rediscover.
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