API Reference

LangGuard exposes a small set of machine-facing APIs. All of them authenticate with an lgr_ API key sent as a bearer token, and the key's scope determines what it may do.

Interceptor API

The policy decision endpoint. Gateways and the Arbiter daemon call it for every MCP tool call and receive an allow, block, or ask verdict. Implements the MCP Interceptors extension (SEP-2624).

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OTLP ingestion

Traces and logs are ingested over standard OpenTelemetry Protocol endpoints using an Ingest-scoped key. See API Keys for the endpoints and headers.

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MCP Server

AI agents can operate LangGuard itself over the Model Context Protocol. See MCP Server for the endpoint, scopes, and available tools.