YaCy peer-to-peer search

yacy-search MCP server

An MCP server for one YaCy peer: web search without a search API or API key, crawling, ranking settings and search quality evaluation. It runs next to the agent (stdio) and talks to the agent's own peer over HTTP. There is no central service: the peer is yours, and it searches the peer-to-peer network it belongs to. Registry name: io.github.pad01g/yacy-search.

It is written for the improved-search fork (results carry author signature verdicts and tags). Search, crawl, status and settings also work with upstream YaCy.

Run

Start a peer and the MCP server on one Docker network:

docker network create yacy 2>/dev/null || truedocker run -d --name yacy --network yacy -p 127.0.0.1:8090:8090 \  -v yacy_data:/opt/yacy_search_server/DATA ghcr.io/pad01g/yacy-improved-search:latest
# Claude Codeclaude mcp add yacy -- docker run -i --rm --network yacy \  -e YACY_URL=http://yacy:8090 -e YACY_ADMIN_PASSWORD='<your password>' ghcr.io/pad01g/yacy-search-mcp:1.0.0

The fork's image starts with the administrator account admin / yacy: change the password at http://127.0.0.1:8090/ConfigAccounts_p.html before connecting the MCP server, and pass the new one.

Other clients (mcp.json style):

{  "mcpServers": {    "yacy": {      "command": "docker",      "args": ["run", "-i", "--rm", "--network", "yacy", "-e", "YACY_URL=http://yacy:8090", "-e", "YACY_ADMIN_PASSWORD=<your password>", "ghcr.io/pad01g/yacy-search-mcp:1.0.0"]    }  }}

For a peer outside Docker use -e YACY_URL=http://host.docker.internal:8090 (Linux: add --add-host=host.docker.internal:host-gateway). Without Docker: npm ci && node src/server.ts in this directory (Node 24).

On the improved-search fork, the vector search (short questions find pages without the exact words) is used only for searches of the peer's administrator or from its host. When the MCP server runs in another container, set search.vector.public=true on the peer (it then embeds every new query of its search page).

Tools

1.0.0 renamed the tools to a consistent verb_noun form (no aliases): search → search_web, crawl → crawl_site, crawls → list_crawls, crawl_control → control_crawl, index_status → get_index_status, peers → list_peers, trust_status → get_trust_status. Clients that call tools by name need the new names.

A typical loop for improving results: evaluate_ranking → set_ranking_setting → evaluate_ranking.

Titles and snippets come from page authors and other peers: the tool descriptions tell the model to treat them as data, not instructions. crawl_site, control_crawl, delete_document and set_ranking_setting are marked destructive so that clients ask before calling them. Values of settings are checked per key, and a value YaCy stores differently is rolled back.

Test

npm ci && npm run typecheck && npm test                      # unit testsYACY_URL=http://localhost:8090 YACY_ADMIN_PASSWORD=yacy npm test   # also calls every tool on a live peer

License

This directory (the MCP server) is under the MIT license. It talks to YaCy only over HTTP and contains no YaCy code; the rest of this repository, YaCy itself, stays under the GPL.