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What is the Model Context Protocol?

AUTHOR · XERJ documentation team · REVIEWED BY · XERJ engineering team · PUBLISHED · 2026-11-13 · UPDATED · 2026-11-14
SHORT ANSWER · UPDATED 2026-11-14

What is the Model Context Protocol? It is an open protocol that lets a host, such as Claude Code or Cursor, call tools on a local or remote node. XERJ exposes search, definition lookup, and memory tools over MCP. 24 tools are listed on main, 21 of them with no Corpus Hub key.

Key number: 24 tools are listed on main, 21 of them with no Corpus Hub key. (as of 2026-10-19 · source: /answers/local-code-search-mcp-fewer-tokens-than-grep)

TL;DR The Model Context Protocol, or MCP, is an open protocol that lets a host such as Claude Code or Cursor call tools on a local or remote node. XERJ exposes search and memory as those tools.

Try it: a tool call, step by step

How an agent reaches XERJ over MCP

  1. 1. The host starts a client

    Claude Code, Cursor, or another host speaks MCP and starts a client.

  2. 2. The client connects to xerj mcp

    xerj mcp exposes tools such as search, definition lookup, and memory tools.

  3. 3. The model picks a tool

    When the question needs retrieval or memory, the model issues a tool call instead of reading a whole tree.

  4. 4. The result comes back cited

    XERJ returns passages or memories with file:line or a namespace, and the model can quote them. 24 tools are listed on main, 21 of them with no Corpus Hub key.

MCP is the open protocol documented at modelcontextprotocol.io. The 24-tool / 21-without-hub-key count is the published figure from the local code-search MCP answer (inspector listing on main, 2026-10-19).
PASTE THIS TO YOUR AI AGENT — IT DOES THE REST Act as a coding agent. Read https://xerj.org/llms.txt, install XERJ, start a local node, index one folder I point you to, and run one search so I can see a cited passage.

How it works

A host starts an MCP client. The client connects to a node that speaks the protocol and advertises a list of tools. When the model needs one of those tools, it issues a tool call. The node runs the tool and returns the result to the host.

The protocol is the contract. It does not itself index your files or store your facts.

How XERJ uses it

xerj mcp exposes tools such as search, definition lookup, and memory tools. The model can retrieve a cited passage or a stored fact instead of reading a whole tree. 24 tools are listed on main, 21 of them with no Corpus Hub key. That count is from the inspector listing on 2026-10-19, published on the local code-search MCP answer.

Memory tools are explained under agentic memory. A how-to for memory over MCP is what is an MCP memory server.

History and research

MCP is documented at the official site, modelcontextprotocol.io. This page uses that site as the protocol reference, and XERJ's published tool count as the product figure. It does not invent a paper for the protocol.

Guides

Guides: code search MCP for Claude Code, local search MCP for Codex and Cursor and MCP code search compared.

Related terms

Agentic memory and syntax-aware search.

FAQ

What is MCP?

The Model Context Protocol is an open protocol for hosts to call tools on a node. The official documentation is at modelcontextprotocol.io.

How does an agent reach XERJ over MCP?

The host starts a client, the client connects to xerj mcp, and the model issues a tool call for search, definition lookup, or memory.

How many tools does XERJ expose?

24 tools are listed on main, 21 of them with no Corpus Hub key. That count is from the inspector listing on 2026-10-19, published on the local code-search MCP answer.

Is MCP a XERJ protocol?

No. MCP is an open protocol. XERJ is one node that speaks it, so an agent can search and store memory without reading a whole tree.

Evidence

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