Arion in front of tools for agents: REST backends, OpenAPI documents and upstream MCP servers exposed as one MCP endpoint, with per-tool authorization, tool search and dynamic discovery. In code mode, agents send one script that composes many tools, and Arion runs it in a sandbox.
MCP Gateway
Serve tools to agents over MCP: REST and OpenAPI backends as tools, federated MCP servers, tool search, code mode, authorization and discovery over xDS.
9 pages
In this group
- MCP gateway overviewHow the MCP gateway filter turns Arion into an MCP server: one endpoint, a registry of namespaced tools, and two ways for agents to use them. Read →
- Tools modeConventional MCP serving: agents list and call tools one at a time, discover a large catalog through tool_search, and call anything they may use by name. Read →
- Code modeServe one execute tool: the agent sends TypeScript that finds, calls and combines tools, and Arion runs it in a sandbox and returns one result. Read →
- Tools and REST backendsDeclare static MCP tools and map tools/call onto HTTP requests: namespaces, path templates, query parameters, body mapping and response handling. Read →
- OpenAPI toolsExpand an OpenAPI 3.x document into one REST-backed MCP tool per operation, with operation filters, one shared policy and live updates over TDS. Read →
- Federating MCP serversPut Arion in front of upstream MCP servers: auto-discover their tools under a namespace, and control disclosure, caching and refresh. Read →
- Tool searchProgressive tool disclosure for agents: eager and progressive tools, the tool_search tool, BM25 and remote-embedding ranking, and the search endpoint. Read →
- Tool authorizationPer-tool RBAC for MCP: allow or deny listing, search, calls and code-mode scripts based on validated JWT claims and header fields. Read →
- Tool discovery over xDS (TDS)Deliver MCP tools, OpenAPI sources, dynamic servers and code-mode toolkits from a control plane: scopes, resource types, and update and remove rules. Read →