MCP is an integration boundary
The official architecture separates host, clients and servers. The host coordinates permissions and context; each client has an isolated server connection; each server exposes focused capabilities.
Host
Manages connections, consent, policy and model integration.
Client
Negotiates capabilities and maintains a server connection.
Server
Exposes tools, resources or prompts under a focused responsibility.
Tool
An action with a schema and effects; it is a security boundary.
A skill turns expertise into procedure
A skill supplies what the protocol does not try to solve: criteria, sequence, templates, checks and task-specific decisions.
- ✓Say when to use it and when not to.
- ✓Define inputs, outputs and acceptance checks.
- ✓Include reusable references or scripts.
- ✓Make destructive actions and permissions explicit.
- ✓Finish with evidence, not an agent claim.
Design the team around responsibility
Adding agents indiscriminately increases coordination, cost and failure surfaces. Split roles when they need different context, tools or criteria.
Coordinator
Turns the objective into work, maintains state and decides when to finish.
Specialists
Build bounded parts with minimum tools.
Verifier
Runs tests or reviews artifacts against independent criteria.
Human
Authorizes high-impact changes and resolves business ambiguity.
Completion conditions rule
A system does not finish because a model says so. It finishes when an artifact exists and passes observable controls.
- ✓Successful build or execution.
- ✓Functional and regression tests.
- ✓Relevant tool and decision log.
- ✓Known limits, cost and failures.
- ✓Escalation when criteria cannot be verified.