What Is an Agentic Semantic Layer?

An agentic semantic layer is a metadata layer between AI agents and a data warehouse that defines business metrics, enforces access control, and exposes governed query interfaces. Instead of writing raw SQL, agents query metric definitions through protocols like MCP (Model Context Protocol) or REST APIs. Every agent gets the same answer because the business logic is defined once, not interpreted per query.

The "agentic" distinction matters. Traditional semantic layers were built for BI dashboards and human analysts. An agentic semantic layer is built for programmatic consumers: LLMs, AI agents, SDKs, and applications. The interface, security model, and deployment patterns are different.

Why do AI agents need one?

AI agents accessing data warehouses via text-to-SQL generate plausible queries from column names. They don't know your business rules. "Revenue" might exclude refunds in finance but include them in marketing. The agent doesn't know which definition to use, so it picks one. Ask a different agent the same question and you get a different number.

Three problems compound in production:

Inconsistent results. Different agents, different prompts, different SQL, different numbers. No source of truth.

No access control. Text-to-SQL has no built-in tenant isolation or RBAC. An agent can query any row it can reach.

No auditability. When the number is wrong, you can't trace it back to a fixed definition because there isn't one. The SQL was generated on the fly.

A semantic layer solves all three. Metrics are defined once. Access rules are enforced on every query. Every result traces back to a versioned definition.

How it differs from a traditional semantic layer

| Traditional semantic layer | Agentic semantic layer
Built for | BI dashboards, analysts | AI agents, LLMs, applications
Interface | SQL, proprietary query language | MCP, REST API, SDK
Multi-tenancy | Often manual or absent | Per-query enforcement, built-in
Access control | Dashboard-level | Row-level, per-consumer
Discovery | Human browses a catalog | Agent calls explore_schema at runtime
Deployment | GUI-configured | YAML in Git, CLI-driven
Caching | Dashboard-level | Pre-aggregation with automatic invalidation

The core shift: an agentic semantic layer treats programmatic access as the primary use case, not an afterthought.

How it works

You define metrics in YAML and deploy them as an API that agents can query.

cubes:
- name: orders
sql_table: public.orders
measures:
- name: total_revenue
sql: "CASE WHEN status != 'refunded' THEN amount ELSE 0 END"
type: sum
- name: order_count
type: count
dimensions:
- name: category
sql: category
type: string
- name: created_at
sql: created_at
type: time

total_revenue is now a governed definition, not a column an agent interprets. Deploy this schema and any MCP-compatible agent (Claude, Cursor, or any client supporting the protocol) can discover and query these metrics at runtime.

The agent calls explore_schema to see available metrics, then query to fetch data with filters. It never writes SQL. The semantic layer handles query generation, execution, caching, and access control.

For a full walkthrough with working code, see How to Connect an AI Agent to Your Data Warehouse.

What to look for

If you're evaluating an agentic semantic layer, the capabilities that matter most:

MCP support. The agent needs a standardized way to discover and query metrics. MCP is the emerging standard for agent-to-tool communication.

Multi-tenancy. B2B products need per-tenant isolation on every query. This should be structural, not a prompt-level filter.

Schema-as-code. Metric definitions in version control. Changes through pull requests. Rollbacks with git revert.

Pre-aggregation. Agents make more queries than humans. Sub-second responses require cached rollups, not full table scans.

Warehouse coverage. At minimum: Snowflake, BigQuery, Databricks, PostgreSQL.

Tools in this space include Cube, AtScale, dbt (metrics layer), and Bonnard (agent-native from the ground up). The right choice depends on whether AI agents are your primary consumer or a secondary integration.

Read more about the broader shift in Why Your AI Agents Need a Semantic Layer and Agentic Analytics.

Frequently asked questions

What is a semantic layer in simple terms?

A semantic layer is a translation layer between raw data and the people or tools that query it. It defines what business terms like "revenue" or "active user" mean in terms of actual database columns and calculations. Instead of every consumer writing its own SQL, they all reference the same definition.

How is an agentic semantic layer different from RAG?

RAG (Retrieval-Augmented Generation) feeds unstructured documents to an LLM for context. An agentic semantic layer provides structured metric definitions for data queries. RAG answers "What does our refund policy say?" A semantic layer answers "What was Q1 revenue?" They solve different problems and are often used together.

Do I need an agentic semantic layer if I use dbt?

dbt defines transformations: how raw data becomes clean tables. A semantic layer defines metrics: what "revenue" means on top of those tables. They're complementary. dbt gets data into shape. The semantic layer defines the business logic on top. Most agentic semantic layers can import dbt models directly.

Can any AI model use an agentic semantic layer?

Yes. A semantic layer with MCP support works with any MCP-compatible client. For other agents, REST APIs and SDKs provide model-agnostic access. The semantic layer sits between the agent and the warehouse, not inside the model.

What is the performance impact of adding a semantic layer?

With pre-aggregation, queries get faster, not slower. The semantic layer caches rollups so agents query pre-computed results instead of running full aggregations on every request. Hot queries resolve in single-digit milliseconds.