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r3 is an MCP server that communicates over standard input and output, not HTTP. Every capability is exposed as a tool. This page covers the transport, the tool-call shape, namespaces, and how responses are returned.

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Transport

Your MCP client launches r3 as a child process and speaks the Model Context Protocol over stdio. Message framing is handled by the MCP SDK. You do not send requests to an HTTP URL. The client manages process lifecycle, initialization, and message boundaries.

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Call format

A tool call uses the tools/call method. Always include arguments, even when the tool has no parameters. Handlers require arguments to be present and will return an error if it is missing.

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Namespaces

MEM0_USER_ID sets the default user namespace for all tool calls. You can override it per call with the user_id argument. Keep your namespace consistent so memories remain retrievable across sessions.

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Modes change the tool list

extract_entities, get_knowledge_graph, and find_connections appear only when INTELLIGENCE_MODE=enhanced (the default). In basic mode, these tools are not registered and will not be discovered by the client.

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Response shape

Responses use MCP content blocks with plain text. Some tools embed serialized JSON inside a text block. Always check isError before parsing the text. If isError is true, the text contains an error message rather than the expected result. For the full tool reference, see Memory Tools, Cache Tools, and Knowledge Graph.
Last modified on September 20, 2026