Evaluation. MCP. Agent Interfaces2026
Tool-semantics
Behavioral Compatibility Testing for MCP Tools
EngineeringResearchProduct
Problem
MCP Tool schemas can stay valid while agent behavior breaks: silent contract drift that unit tests and type checks miss.
Approach
Defined behavioral compatibility checks for MCP Tools and AI agent interfaces beyond static schema validation.
Focused on detecting changes that break agent workflows even when the published schema still type checks.
Treated Tool interfaces as runtime contracts that need regression evidence, not only API documentation.
Results
Schema and behavior. MCP Tool contracts
- A framework for catching agent breaking Tool changes early
- Clearer separation between schema validity and behavioral compatibility
- Practical evaluation surface for MCP Tool evolution
Stack
MCPEvaluationTool CallingTypeScript
Learnings
For agent systems, the interface is incomplete without behavior. A green schema check is not enough when the agent’s Tool use path has shifted.