Fixing AI Observability: How I Added GenAI Semantic Support for RAG Embedding Spans in Mastra

OpenTelemetry has become the standard for observing modern systems. But when you start building AI applications, traditional traces aren't enough. You don't just want to know that a request happened. You want to know: Which model generated the output? Which provider was used? How many tokens were consumed? What embedding model processed the documents? How much did the operation cost? These questions become even more important when building Retrieval-Augmented Generation (RAG) systems. Recently while contributing to Mastra, I discovered an observability gap involving RAG embedding operations. This led me to open a pull request that introduced proper OpenTelemetry GenAI semantic mappings for RAG_EMBEDDING spans. The Problem Mastra already exported rich metadata for several AI operations. However, RAG embedding spans were missing standardized GenAI semantic attributes. As a result, observability tools could see that an embedding operation occurred, but they couldn't easily understand: Model information Provider information Token usage Embedding-specific metadata Without standardized semantic conventions, dashboards and tracing systems lose valuable context. This becomes a bigger issue in production environments where teams need visibility into AI workloads. Understanding RAG Embedding Spans A typical RAG pipeline looks like this: Documents ↓ Chunking ↓ Embedding Model ↓ Vector Database ↓ Similarity Search ↓ LLM Generation The embedding stage is critical. Every document chunk gets transformed into a vector representation. If observability data from this stage is incomplete, debugging performance issues becomes significantly harder. Why OpenTelemetry Semantic Conventions Matter OpenTelemetry doesn't just define traces. It also defines semantic conventions. These conventions create a common language for telemetry data. Instead of every framework inventing custom field names, everyone follows the same standard. For GenAI workloads this means tools can automatically underst