mcp_serve_store: Serve a Ragnar store over MCP

In ragnar: Retrieval-Augmented Generation (RAG) Workflows

Serve a Ragnar store over MCP

Description

Launches an MCP server (via mcptools::mcp_server()) that exposes a retrieval tool backed by a Ragnar store. This lets MCP-enabled clients (e.g., Codex CLI, Claude Code) call into your store to retrieve relevant excerpts.

Usage

mcp_serve_store(
  store,
  store_description = "the knowledge store",
  ...,
  name = NULL,
  title = NULL,
  extra_tools = NULL
)

Arguments

store	A RagnarStore object or a file path to a Ragnar DuckDB store. If a character path is supplied, it is opened with ragnar_store_connect().
store_description	Optional string used in the tool description presented to clients.
...	arguments passed on to ragnar_retrieve().
name, title	Optional tool function name and title. By default, store@name and store@title will be used if present. The tool name must be a valid R function name and should be unique with the tools registered with the ellmer::Chat object. title is used for user-friendly display.
extra_tools	Optional additional tools (list of ellmer::tool() objects) to serve alongside the retrieval tool.

Details

To use this function with Codex CLI, add something like this to ⁠~/.codex/config.toml⁠

[mcp_servers.quartohelp]
command = "Rscript"
args = [
  "-e",
  "ragnar::mcp_serve_store('/path/to/ragnar.store', top_k=10)"
]

You can confirm the agent can search the ragnar store by inspecting the output from the ⁠/mcp⁠ command, or by asking it "What tools do you have available?".

Value

This function blocks the current R process by running an MCP server. It is intended for non-interactive use. Called primarily for side-effects.

ragnar documentation built on Sept. 11, 2026, 1:06 a.m.