fix(memory): use plain JSON Schema for outputSchema instead of Zod

Per the MCP spec, outputSchema must be a plain JSON Schema object.
The memory server was passing Zod schema objects directly, which
causes serialization failures when tools/list attempts to convert
schemas to JSON-RPC responses.

inputSchema still uses Zod for runtime validation (correct usage).
outputSchema now uses plain JSON Schema objects for documentation
and type hints (spec-compliant).

Fixes #3622

Author: Charlie Tonneslan

src/memory/index.ts

@@ -252,6 +252,28 @@ const RelationSchema = z.object({
   relationType: z.string().describe("The type of the relation")
 });
 
+// JSON Schema equivalents for outputSchema (MCP spec requires plain JSON Schema, not Zod)
+const EntityJsonSchema = {
+  type: "object" as const,
+  properties: {
+    name: { type: "string" as const },
+    entityType: { type: "string" as const },
+    observations: { type: "array" as const, items: { type: "string" as const } },
+  },
+  required: ["name", "entityType", "observations"] as const,
+};
+
+const RelationJsonSchema = {
+  type: "object" as const,
+  properties: {
+    from: { type: "string" as const },
+    to: { type: "string" as const },
+    relationType: { type: "string" as const },
+  },
+  required: ["from", "to", "relationType"] as const,
+};
+
+
 // The server instance and tools exposed to Claude
 const server = new McpServer({
   name: "memory-server",
@@ -268,7 +290,10 @@ server.registerTool(
       entities: z.array(EntitySchema)
     },
     outputSchema: {
-      entities: z.array(EntitySchema)
+      type: "object" as const,
+      properties: {
+        entities: { type: "array" as const, items: EntityJsonSchema },
+      },
     }
   },
   async ({ entities }) => {
@@ -290,7 +315,10 @@ server.registerTool(
       relations: z.array(RelationSchema)
     },
     outputSchema: {
-      relations: z.array(RelationSchema)
+      type: "object" as const,
+      properties: {
+        relations: { type: "array" as const, items: RelationJsonSchema },
+      },
     }
   },
   async ({ relations }) => {
@@ -315,10 +343,19 @@ server.registerTool(
       }))
     },
     outputSchema: {
-      results: z.array(z.object({
-        entityName: z.string(),
-        addedObservations: z.array(z.string())
-      }))
+      type: "object" as const,
+      properties: {
+        results: {
+          type: "array" as const,
+          items: {
+            type: "object" as const,
+            properties: {
+              entityName: { type: "string" as const },
+              addedObservations: { type: "array" as const, items: { type: "string" as const } },
+            },
+          },
+        },
+      },
     }
   },
   async ({ observations }) => {
@@ -340,8 +377,11 @@ server.registerTool(
       entityNames: z.array(z.string()).describe("An array of entity names to delete")
     },
     outputSchema: {
-      success: z.boolean(),
-      message: z.string()
+      type: "object" as const,
+      properties: {
+        success: { type: "boolean" as const },
+        message: { type: "string" as const },
+      },
     }
   },
   async ({ entityNames }) => {
@@ -366,8 +406,11 @@ server.registerTool(
       }))
     },
     outputSchema: {
-      success: z.boolean(),
-      message: z.string()
+      type: "object" as const,
+      properties: {
+        success: { type: "boolean" as const },
+        message: { type: "string" as const },
+      },
     }
   },
   async ({ deletions }) => {
@@ -389,8 +432,11 @@ server.registerTool(
       relations: z.array(RelationSchema).describe("An array of relations to delete")
     },
     outputSchema: {
-      success: z.boolean(),
-      message: z.string()
+      type: "object" as const,
+      properties: {
+        success: { type: "boolean" as const },
+        message: { type: "string" as const },
+      },
     }
   },
   async ({ relations }) => {
@@ -410,8 +456,11 @@ server.registerTool(
     description: "Read the entire knowledge graph",
     inputSchema: {},
     outputSchema: {
-      entities: z.array(EntitySchema),
-      relations: z.array(RelationSchema)
+      type: "object" as const,
+      properties: {
+        entities: { type: "array" as const, items: EntityJsonSchema },
+        relations: { type: "array" as const, items: RelationJsonSchema },
+      },
     }
   },
   async () => {
@@ -433,8 +482,11 @@ server.registerTool(
       query: z.string().describe("The search query to match against entity names, types, and observation content")
     },
     outputSchema: {
-      entities: z.array(EntitySchema),
-      relations: z.array(RelationSchema)
+      type: "object" as const,
+      properties: {
+        entities: { type: "array" as const, items: EntityJsonSchema },
+        relations: { type: "array" as const, items: RelationJsonSchema },
+      },
     }
   },
   async ({ query }) => {
@@ -456,8 +508,11 @@ server.registerTool(
       names: z.array(z.string()).describe("An array of entity names to retrieve")
     },
     outputSchema: {
-      entities: z.array(EntitySchema),
-      relations: z.array(RelationSchema)
+      type: "object" as const,
+      properties: {
+        entities: { type: "array" as const, items: EntityJsonSchema },
+        relations: { type: "array" as const, items: RelationJsonSchema },
+      },
     }
   },
   async ({ names }) => {