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Version: 1.1.x

Consumer Tags

MCPX lets clients identify themselves using the x-lunar-consumer-tag HTTP header. This enables fine-grained control over access, rate limiting, and observability.

A consumer is any client connecting to MCPX, usually an app or service working with LLMs that calls one or more tools through MCPX.

A consumer group is a logical label for requests from related consumers, e.g. a team, environment, or use case.

Why Use Consumer Tags?​

In AI and multi-agent systems, request context can be hard to pin down. Tags give you a reliable way to group and control traffic.

You can use them to:

  • Distinguish between teams or environments (team:alpha, env:prod)
  • Apply ACLs to restrict access by tag
  • Define rate limits per group
  • Add structured metadata to logs and dashboards

Tag Format​

Tags are passed as a single HTTP header:

x-lunar-consumer-tag: key:value
x-lunar-consumer-tag: env:staging

Consumer Tags are:

  • Optional but highly recommended for most production use cases
  • Flexible, allowing you to define any keys that make sense for your organization
  • Used across features including ACLs, quotas, and observability