An MCP Server Is Not Interoperable Just Because It Connects

Description and use

MCP server testing must verify schema, error state, concise content, and structured data, not just connectivity.

Problem

MCP handshake only confirms connection; it does not guarantee that the client can correctly use the tool, interpret responses, or detect errors.

Outcome

The smoke test confirms that the server advertises the correct schema, returns non‑error responses, provides concise content, and supplies deterministic structured data, ensuring better interoperability.

Workflow

• 1. Call list_tools() and inspect input schema for each tool.
• 2. Verify CallToolResult.is_error is false for a sample call.
• 3. Check that content contains concise summary without full payload.
• 4. Inspect structured_content for required fields (response_type, completion, assistant_action, normalized locations, etc.).

Evidence

The test call returned is_error=false.

Source

The structured result carried destination normalization, product fields and workflow state.

Source