Store, query, and manage a knowledge graph (entities, relations, observations) via @modelcontextprotocol/server-memory (npx) — Anthropic reference server, 9 tools

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## @modelcontextprotocol/server-memory v2026.1.26 — Verified Recipe

**Package:** `@modelcontextprotocol/server-memory` (Anthropic official reference server)
**Install:** `npm install @modelcontextprotocol/server-memory`
**Entry:** `dist/index.js` — runs on stdio, persists graph to JSON file in working directory
**Version tested:** 2026.1.26

### Tools (9)

| Tool | Params | Description |
|------|--------|-------------|
| `create_entities` | `entities: [{name, entityType, observations[]}]` | Create entities with typed observations |
| `create_relations` | `relations: [{from, to, relationType}]` | Create directional relations between entities |
| `add_observations` | `observations: [{entityName, contents[]}]` | Add observations to existing entities |
| `delete_entities` | `entityNames: string[]` | Delete entities and cascade-delete their relations |
| `delete_observations` | `deletions: [{entityName, observations[]}]` | Remove specific observations |
| `delete_relations` | `relations: [{from, to, relationType}]` | Remove specific relations |
| `read_graph` | (none) | Return full graph: all entities + relations |
| `search_nodes` | `query: string` | Search across entity names, types, and observations |
| `open_nodes` | `names: string[]` | Open specific entities with inter-relations |

### Execution trace — 26 calls, 100% success

**Session 1 — Full CRUD lifecycle (14 calls):**
1. `create_entities` — 3 entities (TypeScript/Language, Rust/Language, WebAssembly/Technology) with 2 observations each → returned all 3 with observations
2. `create_relations` — 2 relations (TypeScript→WebAssembly compiles_to, Rust→WebAssembly compiles_to) → returned both
3. `read_graph` — full graph with 3 entities + 2 relations
4. `search_nodes("memory safe")` — **returned EMPTY** despite "Memory-safe systems language" observation existing (see gotcha below)
5. `open_nodes(["TypeScript"])` — returned entity WITHOUT relations (relations only show when both endpoints opened)
6. `add_observations` — added 2 new observations to TypeScript → returned `{entityName, addedObservations}`
7. `search_nodes("Angular")` — found TypeScript (matched newly added observation)
8. `delete_relations` — removed TypeScript→WebAssembly → "Relations deleted successfully"
9. `delete_observations` — removed "No garbage collector" from Rust → "Observations deleted successfully"
10. `read_graph` — confirmed: Rust has 1 observation, only Rust→WebAssembly relation remains
11. `delete_entities(["WebAssembly"])` — "Entities deleted successfully" + cascade-deleted Rust→WebAssembly relation
12. `read_graph` — 2 entities (TypeScript, Rust), 0 relations
13. `search_nodes("Python")` — empty result (correct)

**Session 2 — Edge cases (12 calls):**
14. Setup: create React/Framework + Node.js/Runtime + relation
15. **Duplicate entity**: `create_entities` with same name "React" + new observation → returned `[]` (empty). **Observation NOT merged** — duplicates are silently ignored, not merged. Use `add_observations` to add to existing entities.
16. `open_nodes(["React"])` — confirmed only original 2 observations (no merge)
17-19. **Search case sensitivity**: "virtual dom", "VIRTUAL DOM", "Virtual DOM" all found 1 entity → **search is CASE-INSENSITIVE**
20. `search_nodes("React")` — 1 entity → search matches **entity names** too
21. `search_nodes("Runtime")` — 1 entity → search matches **entityType** too
22. `open_nodes(["Python", "Go"])` — `{entities:[], relations:[]}` → graceful empty for non-existent
23. `open_nodes(["React", "Node.js"])` — returned BOTH entities AND the relation between them → **relations only appear when both endpoints are in the opened set**
24. `delete_entities(["Python"])` — "Entities deleted successfully" → **idempotent delete** (no error for non-existent)
25. `search_nodes("")` — returned 4 entities → **empty query returns ALL entities**
26. Data persisted across server restarts (same working directory)

### Key gotchas

1. **⚠️ Duplicate entities are SILENTLY IGNORED*

Tool	Params	Description
`create_entities`	`entities: [{name, entityType, observations[]}]`	Create entities with typed observations
`create_relations`	`relations: [{from, to, relationType}]`	Create directional relations between entities
`add_observations`	`observations: [{entityName, contents[]}]`	Add observations to existing entities
`delete_entities`	`entityNames: string[]`	Delete entities and cascade-delete their relations
`delete_observations`	`deletions: [{entityName, observations[]}]`	Remove specific observations
`delete_relations`	`relations: [{from, to, relationType}]`	Remove specific relations
`read_graph`	(none)	Return full graph: all entities + relations
`search_nodes`	`query: string`	Search across entity names, types, and observations
`open_nodes`	`names: string[]`	Open specific entities with inter-relations

Store, query, and manage a knowledge graph (entities, relations, observations) via @modelcontextprotocol/server-memory (npx) — Anthropic reference server, 9 tools

@modelcontextprotocol/server-memory v2026.1.26 — Verified Recipe

Tools (9)

Execution trace — 26 calls, 100% success

Key gotchas

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