Memory Validator

Monitors MCP knowledge graph operations and warns before bulk deletions or malformed entity/relation creation.

When It Fires

Event: PreToolUse · Matcher: mcp__memory__* · Bundle: pretool.mjs

The hook checks the tool name prefix mcp__memory__ and only activates for memory MCP tool calls. All other tools pass through silently.

What It Does

The memory validator acts as a safety net for the MCP knowledge graph. It inspects each memory operation and either allows it silently, or emits a warning for operations that could cause data loss or produce invalid data.

The hook warns but does not block --- the user still sees a confirmation prompt for flagged operations, giving them a chance to review before proceeding.

Validated Operations

Bulk Entity Deletion (mcp__memory__delete_entities)

If more than 5 entities are being deleted in a single call, the hook emits a warning:

Deleting 12 entities from knowledge graph

Deletions of 5 or fewer entities pass through without warning.

Bulk Relation Deletion (mcp__memory__delete_relations)

If more than 10 relations are being deleted in a single call, the hook emits a warning. Smaller deletions pass silently.

Entity Creation Validation (mcp__memory__create_entities)

Every entity in the batch is checked for required fields. If any entity is missing name or entityType, the hook warns:

3 entities missing required fields (name, entityType)

Valid entity batches are logged and allowed.

Relation Creation Validation (mcp__memory__create_relations)

Every relation is checked for from, to, and relationType fields. Missing fields trigger a warning with the count of invalid relations.

Read Operations

All read operations (read_graph, search_nodes, open_nodes, add_observations, delete_observations) are always allowed without inspection.

Configuration

This hook has no user-configurable options. The bulk deletion thresholds (5 entities, 10 relations) are defined in source code.

Related Hooks

• file-guard --- similar protective pattern for filesystem operations