Graph Context & Debugging System — Schema Retrieval via MCP
A context retrieval system that ingests and indexes schema from a centralized schema store, surfacing historical evolution data to support debugging and reduce time spent identifying breaking changes across distributed services.
Problem
Debugging breaking changes in a federated GraphQL system requires understanding how a schema evolved over time — which fields were added, removed, or modified, and when. That history was stored in a centralized schema store but was not surfaced in a way that was useful during active debugging.
Engineers had to manually trace schema history across services, which was slow and error-prone, especially when a breaking change had been introduced several versions back.
High Level
Built a context retrieval system using MCP that connects directly to the centralized schema store:
- Ingests and indexes schema history across all registered subgraphs
- Enables querying of schema evolution by service, field, or time range
- Surfaces historical context — prior versions, change diffs, deprecation history — directly into the debugging workflow
- Reduces the manual tracing required to identify when and where a breaking change was introduced
Design Decisions
1. MCP as the integration layer Using MCP to connect the retrieval system to the schema store kept the integration decoupled from the schema store’s internal structure. The system queries through a defined protocol rather than directly coupling to storage internals, making it easier to adapt as the schema store evolves.
2. Index schema history, not just current state Most tooling surfaces only the current schema. The key insight here was that debugging requires the historical delta — not just what the schema is now, but what changed and when. Indexing history rather than snapshotting current state made the system genuinely useful for root cause analysis.
Impact
Reduced the time required to identify breaking changes across distributed services by surfacing schema evolution history directly into the debugging context. Eliminated the need to manually cross-reference schema versions across multiple services during incident investigation.