fix(memory): include type field in output schemas to fix validation error

The memory server stores entities with a 'type' field in JSONL, but the
tool output schemas did not include this property. When structured output
validation is enabled, this causes MCP error -32602 for read_graph,
search_nodes, and open_nodes tools.

Fixes #3074

Author: aayushbaluni

src/memory/__tests__/knowledge-graph.test.ts

@@ -426,7 +426,7 @@ describe('KnowledgeGraphManager', () => {
       expect(JSON.parse(lines[1])).toHaveProperty('type', 'relation');
     });
 
-    it('should strip type field from entities when loading from file', async () => {
+    it('should preserve JSONL type discriminator when loading from file', async () => {
       // Create entities and relations (these get saved with type field)
       await manager.createEntities([
         { name: 'Alice', entityType: 'person', observations: ['test observation'] },
@@ -451,26 +451,25 @@ describe('KnowledgeGraphManager', () => {
       const manager2 = new KnowledgeGraphManager(testFilePath);
       const graph = await manager2.readGraph();
 
-      // Verify loaded entities don't have type field
+      // Loaded graph mirrors JSONL discriminators for structured-output validation (#3074)
       expect(graph.entities).toHaveLength(2);
       graph.entities.forEach(entity => {
-        expect(entity).not.toHaveProperty('type');
+        expect(entity).toHaveProperty('type', 'entity');
         expect(entity).toHaveProperty('name');
         expect(entity).toHaveProperty('entityType');
         expect(entity).toHaveProperty('observations');
       });
 
-      // Verify loaded relations don't have type field
       expect(graph.relations).toHaveLength(1);
       graph.relations.forEach(relation => {
-        expect(relation).not.toHaveProperty('type');
+        expect(relation).toHaveProperty('type', 'relation');
         expect(relation).toHaveProperty('from');
         expect(relation).toHaveProperty('to');
         expect(relation).toHaveProperty('relationType');
       });
     });
 
-    it('should strip type field from searchNodes results', async () => {
+    it('should include type discriminator in searchNodes results after reload', async () => {
       await manager.createEntities([
         { name: 'Alice', entityType: 'person', observations: ['works at Acme'] },
       ]);
@@ -482,17 +481,16 @@ describe('KnowledgeGraphManager', () => {
       const manager2 = new KnowledgeGraphManager(testFilePath);
       const result = await manager2.searchNodes('Alice');
 
-      // Verify search results don't have type field
       expect(result.entities).toHaveLength(1);
-      expect(result.entities[0]).not.toHaveProperty('type');
+      expect(result.entities[0]).toHaveProperty('type', 'entity');
       expect(result.entities[0].name).toBe('Alice');
 
       expect(result.relations).toHaveLength(1);
-      expect(result.relations[0]).not.toHaveProperty('type');
+      expect(result.relations[0]).toHaveProperty('type', 'relation');
       expect(result.relations[0].from).toBe('Alice');
     });
 
-    it('should strip type field from openNodes results', async () => {
+    it('should include type discriminator in openNodes results after reload', async () => {
       await manager.createEntities([
         { name: 'Alice', entityType: 'person', observations: [] },
         { name: 'Bob', entityType: 'person', observations: [] },
@@ -505,14 +503,13 @@ describe('KnowledgeGraphManager', () => {
       const manager2 = new KnowledgeGraphManager(testFilePath);
       const result = await manager2.openNodes(['Alice', 'Bob']);
 
-      // Verify open results don't have type field
       expect(result.entities).toHaveLength(2);
       result.entities.forEach(entity => {
-        expect(entity).not.toHaveProperty('type');
+        expect(entity).toHaveProperty('type', 'entity');
       });
 
       expect(result.relations).toHaveLength(1);
-      expect(result.relations[0]).not.toHaveProperty('type');
+      expect(result.relations[0]).toHaveProperty('type', 'relation');
     });
   });
 });

src/memory/index.ts

@@ -48,12 +48,14 @@ let MEMORY_FILE_PATH: string;
 
 // We are storing our memory using entities, relations, and observations in a graph structure
 export interface Entity {
+  type?: "entity";
   name: string;
   entityType: string;
   observations: string[];
 }
 
 export interface Relation {
+  type?: "relation";
   from: string;
   to: string;
   relationType: string;
@@ -76,13 +78,15 @@ export class KnowledgeGraphManager {
         const item = JSON.parse(line);
         if (item.type === "entity") {
           graph.entities.push({
+            type: "entity",
             name: item.name,
             entityType: item.entityType,
             observations: item.observations
           });
         }
         if (item.type === "relation") {
           graph.relations.push({
+            type: "relation",
             from: item.from,
             to: item.to,
             relationType: item.relationType
@@ -241,12 +245,14 @@ let knowledgeGraphManager: KnowledgeGraphManager;
 
 // Zod schemas for entities and relations
 const EntitySchema = z.object({
+  type: z.literal("entity").optional().describe('Discriminator when parsed from JSONL; omit when creating entities'),
   name: z.string().describe("The name of the entity"),
   entityType: z.string().describe("The type of the entity"),
   observations: z.array(z.string()).describe("An array of observation contents associated with the entity")
 });
 
 const RelationSchema = z.object({
+  type: z.literal("relation").optional().describe('Discriminator when parsed from JSONL; omit when creating relations'),
   from: z.string().describe("The name of the entity where the relation starts"),
   to: z.string().describe("The name of the entity where the relation ends"),
   relationType: z.string().describe("The type of the relation")