MCP-to-MCP: Composing Cross-System Workflows
One MCP server calls another to compose a cross-system workflow — transparent to the calling agent, which sees a single governed tool interface.
What Is the MCP-to-MCP Pattern?
The MCP-to-MCP pattern occurs when one MCP server calls another MCP server to compose a cross-system workflow. Server A receives a tool call from an agent, executes part of the workflow, then calls tools on Server B to complete it — all transparently from the agent's perspective.
When to Use It
- A business process inherently spans two systems but you want to expose it as a single tool to agents
- You want to reuse existing MCP servers rather than duplicating their logic in a new server
- The Orchestration-Federated pattern is overkill for your use case, but cross-server calls are needed
Design Considerations
Error propagation: When Server B fails, Server A must handle the failure gracefully and return a meaningful error to the calling agent. Don't let Server B's error propagate as an opaque failure.
Credential management: Server A calling Server B needs its own credential for Server B — the agent's credential doesn't flow through the chain. Each server-to-server call authenticates independently.
Audit trail continuity: Workato's Control Plane logs cross-server calls with a correlation ID that connects them in the audit trail. Ensure both servers are on the same platform so this continuity is maintained.