MCP vs CAP: Why Your AI Agents Need Both Protocols

What MCP Actually Does

MCP (Model Context Protocol) is a tool-calling protocol for a single model, standardizing how an LLM discovers and invokes external tools like databases and APIs. It solves tool discovery, schema negotiation, and invocation within a single model context.

MCP was never designed for distributed agent orchestration, job scheduling, safety policies, or handling agent liveness—tasks requiring a broader control plane.

Why This Matters

The current explosion of AI agent protocols often conflates tool interaction with distributed orchestration. Using MCP for complex workflows is akin to using HTTP for job scheduling – an inappropriate tool for the task. This mismatch leads to scalability issues, security vulnerabilities, and operational complexity, potentially costing engineering teams significant time and resources.

Key Insights

• MCP focuses on layer 7 (tool execution): It handles communication between a model and its tools.
• CAP addresses layers 5-6 (agent orchestration): It manages job lifecycle, routing, safety, and state across a cluster of agents.
• Cordum developed CAP: CAP is an open-source, cluster-native job protocol for AI agents, available with SDKs for multiple languages.

Working Example

nc, _ := nats.Connect("nats://127.0.0.1:4222")
nc.QueueSubscribe("job.echo", "job.echo", func(msg *nats.Msg) {
var pkt agentv1.BusPacket
proto.Unmarshal(msg.Data, &pkt)
req := pkt.GetJobRequest()
res := &agentv1.JobResult{
JobId: req.GetJobId(),
Status: agentv1.JobStatus_JOB_STATUS_SUCCEEDED,
}
out, _ := proto.Marshal(&agentv1.BusPacket{
Payload: &agentv1.BusPacket_JobResult{JobResult: res},
})
nc.Publish("sys.job.result", out)
})

Practical Applications

• Stripe: Could use CAP for managing complex financial transactions across multiple agents, with MCP handling individual API calls to banking systems.
• Pitfall: Attempting to build a distributed workflow solely with MCP results in brittle, unscalable systems lacking centralized control and safety mechanisms.

References:

• https://dev.to/yaron_torgeman_104570d968/-mcp-vs-cap-why-your-ai-agents-need-both-protocols-3g4l
• https://github.com/cordum-io/cap
• https://github.com/cordum-io/cap/tree/main/spec
• https://github.com/cordum-io/cap