Remove prefix on over-the-wire ProtocolErrors (#1727)

Co-authored-by: Felix Weinberger <3823880+felixweinberger@users.noreply.github.com>

Author: KKonstantinov

packages/core/src/types/types.ts

@@ -2340,7 +2340,7 @@ export class ProtocolError extends Error {
         message: string,
         public readonly data?: unknown
     ) {
-        super(`MCP error ${code}: ${message}`);
+        super(message);
         this.name = 'ProtocolError';
     }
 

test/integration/test/server.test.ts

@@ -809,7 +809,7 @@ test('should wrap unexpected validator errors during elicitInput', async () => {
                 required: []
             }
         })
-    ).rejects.toThrow('MCP error -32603: Error validating elicitation response: boom - validator exploded');
+    ).rejects.toThrow('Error validating elicitation response: boom - validator exploded');
 });
 
 test('should forward notification options when using elicitation completion notifier', async () => {

test/integration/test/server/elicitation.test.ts

@@ -841,7 +841,7 @@ function testElicitationFlow(validatorProvider: typeof ajvProvider | typeof cfWo
                     required: ['color']
                 }
             })
-        ).rejects.toThrow(/^MCP error -32602: Elicitation response content does not match requested schema/);
+        ).rejects.toThrow(/^Elicitation response content does not match requested schema/);
     });
 
     test(`${validatorName}: should reject invalid selection in single-select titled enum`, async () => {
@@ -875,7 +875,7 @@ function testElicitationFlow(validatorProvider: typeof ajvProvider | typeof cfWo
                     required: ['color']
                 }
             })
-        ).rejects.toThrow(/^MCP error -32602: Elicitation response content does not match requested schema/);
+        ).rejects.toThrow(/^Elicitation response content does not match requested schema/);
     });
 
     test(`${validatorName}: should reject invalid selection in single-select titled legacy enum`, async () => {
@@ -906,7 +906,7 @@ function testElicitationFlow(validatorProvider: typeof ajvProvider | typeof cfWo
                     required: ['color']
                 }
             })
-        ).rejects.toThrow(/^MCP error -32602: Elicitation response content does not match requested schema/);
+        ).rejects.toThrow(/^Elicitation response content does not match requested schema/);
     });
 
     // Enums - Invalid - Multi Select - Untitled / Titled
@@ -943,7 +943,7 @@ function testElicitationFlow(validatorProvider: typeof ajvProvider | typeof cfWo
                     required: ['color']
                 }
             })
-        ).rejects.toThrow(/^MCP error -32602: Elicitation response content does not match requested schema/);
+        ).rejects.toThrow(/^Elicitation response content does not match requested schema/);
     });
 
     test(`${validatorName}: should reject invalid selection in multi-select titled enum`, async () => {
@@ -981,6 +981,6 @@ function testElicitationFlow(validatorProvider: typeof ajvProvider | typeof cfWo
                     required: ['colors']
                 }
             })
-        ).rejects.toThrow(/^MCP error -32602: Elicitation response content does not match requested schema/);
+        ).rejects.toThrow(/^Elicitation response content does not match requested schema/);
     });
 }