mcp-server-evolutiondb 1.1.3

MCP (Model Context Protocol) server backed by EvolutionDB — gives Claude Desktop / Claude Code persistent long-term memory.

mcp-server-evolutiondb

A Model Context Protocol server that gives Claude Desktop / Claude Code persistent long-term memory backed by EvolutionDB. Anything Claude decides to remember during a conversation is written to a real database; in any future session — same window or weeks later — Claude can search it back without you having to repaste context.

Install

pipx install mcp-server-evolutiondb
# or:  pip install --user mcp-server-evolutiondb

The package installs the mcp-server-evolutiondb console entry-point (also aliased as mcp-server-evosql). It speaks the PostgreSQL wire protocol over psycopg, so installation is pure-Python — no C toolchain, no libevosql-memory.so to build. EvolutionDB still has to be running somewhere reachable; docker compose up -d in the main repo is the easiest way.

   ┌──────────────────┐         ┌─────────────────────┐         ┌────────────────┐
   │  Claude Desktop  │  stdio  │  mcp-server-evosql  │  TCP    │   EvolutionDB  │
   │   (or Claude     │ ◀──────▶│  (this package)     │ ◀──────▶│  (port 9967)   │
   │     Code)        │  JSON-  │                     │         │                │
   │                  │   RPC    │  save_memory       │         │ MEMORY STORE   │
   │                  │   2.0    │  search_memory     │         │ ENTITY STORE   │
   │                  │          │  recent_memories   │         │                │
   │                  │          │  forget            │         │                │
   │                  │          │  list_tags         │         │                │
   └──────────────────┘          └─────────────────────┘         └────────────────┘

Why

The default Claude experience is stateless — every new chat starts from scratch, so you waste tokens re-explaining who you are, what project you're on, what your preferences are. Plug this server in and the model:

• saves preferences / decisions / facts during natural conversation,
• searches them back the next time you ask something related,
• forgets entries on demand,
• never sees the user_id that pins the namespace (we override it server-side, so the model can't accidentally fragment the namespace by inventing IDs across sessions).

Token math: 100 chats × 3,000 tokens of pre-loaded context (~$0.90 on Sonnet) → 100 chats × 250 tokens of just-relevant facts pulled on demand ($0.26). Roughly 3.5× cheaper inputs without losing context fidelity.

What's exposed to Claude

Five tools, all under one evolutiondb-memory MCP server:

Tool	Purpose
save_memory	Persist a fact + optional tags
search_memory	Substring + tag search (use before answering)
recent_memories	Last N saved facts (most-recent-first)
forget	Delete by key
list_tags	All distinct tags in use, with counts

Each call's user_id is overridden server-side from the MCP_USER_ID env var — stops the model from drifting the namespace across "user" / "default_user" / your name etc.

Install + run

1. Bring up EvolutionDB

cd /path/to/evolutiondb
docker compose up -d

2. Build the SDK once

make -C client/libevosql-memory

3. Configure Claude Desktop

Open the config file:

• macOS: ~/Library/Application Support/Claude/claude_desktop_config.json
• Windows: %APPDATA%\Claude\claude_desktop_config.json

Drop in the entry from examples/claude_desktop_config.json, substituting the absolute paths for your machine. Quit + restart Claude Desktop.

You'll see a small 🔌 / hammer icon in the bottom-right of the chat composer once evolutiondb-memory is connected.

4. Talk normally

Say "remember that I take my espresso single-shot, no sugar"; Claude will run save_memory(...). Days later open a new chat, ask "what do I drink?" — Claude runs search_memory(...) and recalls.

Same setup for Claude Code

If you use Claude Code (the CLI), drop the same mcpServers entry into ~/.claude/mcp.json:

mkdir -p ~/.claude
cp client/mcp-server-evosql/examples/claude_desktop_config.json ~/.claude/mcp.json
# edit the absolute paths

Claude Code picks it up automatically on the next claude invocation.

Configuration

Env var	Default	Purpose
EVOSQL_HOST	127.0.0.1	DB host
EVOSQL_PORT	9967	EVO port
EVOSQL_USER	admin	DB user
EVOSQL_PASSWORD	admin	DB password
MCP_USER_ID	default_user	Sticky namespace for every tool call
MCP_STORE_PREFIX	mcp	Catalog object prefix
EVOSQL_PYTHON_SDK	(auto-discovered)	Override path to the Python ctypes binding
EVOSQL_MEMORY_LIB	(auto-discovered)	Override path to libevosql-memory.dylib/so

Tests

cd client/mcp-server-evosql
python3 tests/test_mcp.py

Eight cases — initialize handshake, tools/list discovery, save+search round-trip, tag-filtered search, recent ordering, forget, list_tags aggregation, and the "user_id can't be hijacked from the LLM side" isolation case. Each test spawns the server as a real subprocess and talks JSON-RPC, so framing bugs that an in-process unit test would hide get caught.

Inspect the database directly

While Claude is using the server, open another terminal and:

docker compose exec evosql evosql-cli -W admin

Then:

SELECT mem_namespace, mem_key, mem_value FROM __mem_mcp_mem;
ENTITY RANK FROM mcp_ents;

Everything Claude has decided to remember is right there as queryable rows — no opaque blob storage.

Wire format

Newline-delimited JSON-RPC 2.0 over stdio (no Content-Length headers — that's the LSP variant; MCP uses plain \n-delimited). The server speaks protocol version 2024-11-05.

{"jsonrpc":"2.0","id":1,"method":"initialize",
 "params":{"protocolVersion":"2024-11-05","capabilities":{}}}

{"jsonrpc":"2.0","id":2,"method":"tools/list"}

{"jsonrpc":"2.0","id":3,"method":"tools/call",
 "params":{"name":"save_memory",
           "arguments":{"fact":"loves jazz","tags":["preference"]}}}

Errors come back as {"jsonrpc":"2.0","id":N,"error":{"code":..,"message":..}} or as a tools/call result with isError: true.

Known limitations

• Single-process EvolutionDB connection. The server holds one Connection — the SDK contract is one-per-thread, and MCP stdio is inherently single-threaded so this is fine.
• No streaming responses. Tool results return as single JSON blobs. Larger memories (>100 facts) take ~50 ms to serialise; the protocol can stream but Claude's tool-use UI doesn't render partial responses anyway.
• Authentication via env-vars only. If you expose the server to another machine (which you shouldn't — it's stdio), set EVOSQL_PASSWORD accordingly. The server doesn't rotate secrets.