API gateways are the control plane of enterprise integration. They handle authentication, rate limiting, routing, and observability for service-to-service communication. But agentic workloads break the assumptions that traditional gateways were built on.
An agent doesn’t make a single stateless request. It holds a session, chains tool calls, builds context across interactions, and consumes resources in patterns that look nothing like human-driven API traffic. The gateway patterns that work for microservices need significant adaptation for the agentic era.
Why traditional gateways fall short
Three fundamental mismatches exist between traditional API gateways and agentic workloads:
Stateless vs. stateful. REST gateways assume each request is independent. Agents maintain sessions across dozens of tool calls, and each call’s context depends on previous results. A gateway that can’t track session identity can’t enforce per-session rate limits or aggregate session-level metrics.
Predictable vs. variable resource consumption. Traditional API traffic has relatively stable per-request resource profiles. An agent’s token consumption varies by 10x or more depending on task complexity, making static rate limits either too restrictive or too permissive.
Single-hop vs. fan-out. A typical API request hits one backend service. An agent request might trigger 10 tool calls across 5 different MCP servers before returning a single response. Gateways need to handle this fan-out pattern without losing observability.
Four gateway patterns for agents
Pattern 1: MCP gateway proxy
The most common pattern. A reverse proxy sits between agents and MCP servers, providing a single endpoint that handles discovery, authentication, and routing across all available tools.
What it provides:
- Centralized authentication and credential management
- Tool discovery aggregation across multiple MCP servers
- Request-level rate limiting and throttling
- Basic request/response logging
What it doesn’t provide:
- Session-level cost tracking
- Semantic understanding of tool call sequences
- Quality-of-service differentiation between agent types
Best for: Organizations with multiple MCP servers that need a unified access layer without deep behavioral governance.
Pattern 2: Token-aware gateway
Extends the proxy pattern with token-level awareness. The gateway inspects LLM request and response payloads to track token consumption, enforce token budgets, and attribute costs.
What it provides:
- Per-agent, per-session token budget enforcement
- Real-time cost attribution by team, use case, or customer
- Token-based rate limiting (tokens per minute, not just requests per minute)
- Cost anomaly detection and alerting
What it doesn’t provide:
- Reasoning quality assessment
- Tool selection governance
- Output validation
Best for: Organizations where cost management is the primary concern and agents consume significant LLM resources.
Pattern 3: Semantic gateway
The most sophisticated pattern. The gateway understands the semantic content of agent requests—not just routing metadata—and applies policies based on what the agent is trying to do.
What it provides:
- Intent-based routing (matching agent requests to optimal tool providers)
- Policy enforcement based on action type (read vs. write vs. delete)
- Automatic tool versioning and compatibility management
- Response validation against expected schemas
What it doesn’t provide:
- Full agent orchestration
- Cross-agent workflow management
- Autonomous governance decisions
Best for: Mature organizations with complex tool landscapes that need fine-grained control over agent behavior at the gateway level.
Pattern 4: A2A federation gateway
Purpose-built for multi-agent environments. This gateway manages Agent Card registries, routes inter-agent communication, and enforces trust policies across organizational boundaries.
What it provides:
- Agent Card registry and discovery services
- Cross-organization trust policy enforcement
- Task lifecycle visibility across agent interactions
- Artifact routing and transformation
What it doesn’t provide:
- Intra-agent tool call governance (that’s the MCP gateway’s job)
- Model-level token management
- Single-agent debugging
Best for: Organizations deploying multi-agent architectures or collaborating with external agent providers across organizational boundaries.
Combining patterns
In practice, most enterprises will need a combination. A common deployment architecture uses:
- An MCP gateway proxy for internal tool access
- A token-aware layer for cost management
- An A2A federation gateway at organizational boundaries
These can be implemented as separate infrastructure or as layers within a single gateway platform—the architectural choice depends on your operational maturity and traffic patterns.
Implementation considerations
Start with the proxy pattern. MCP gateway proxy is the lowest-risk, highest-value starting point. It provides immediate benefits—centralized auth, basic observability, simplified tool discovery—without requiring deep integration.
Instrument before you enforce. Spend time observing agent traffic patterns before setting rate limits or token budgets. Agent behavior is often surprising, and premature policy enforcement creates friction without reducing risk.
Plan for session affinity. If your agents maintain state across tool calls, your gateway needs session awareness. This has infrastructure implications for load balancing and horizontal scaling.
Design for fan-out. Agent requests that trigger multiple downstream tool calls need careful timeout management. A single slow MCP server shouldn’t block an entire agent session.
The bigger picture
API gateways for agentic workloads aren’t a new product category—they’re an evolution of existing infrastructure to handle new traffic patterns. The fundamental gateway capabilities (auth, rate limiting, routing, observability) remain essential. What changes is the granularity and intelligence required at each layer.
The organizations that adapt their gateway strategy for agentic workloads will maintain the governance and visibility they need. Those that try to force agentic traffic through traditional gateway patterns will find their control plane increasingly irrelevant.