Siftdog MCP Server

Siftdog — open-source, self-hosted Tavily alternative

Siftdog is an open-source, self-hosted web search API for AI agents and LLM apps, and a drop-in replacement for the Tavily API. It serves the same /search, /extract, /crawl and /map endpoints with the same request and response shapes, so code written for Tavily (including the official Python SDK and the LangChain integration) works against your own server by changing only the base URL. It needs no search API key. Website: siftdog.com.

• Search through a SearXNG metasearch instance, with no search API keys
• Extraction of clean markdown or text from web pages with trafilatura
• Ranking: BM25 relevance blended with the upstream engine's order; advanced depth fetches each page and returns its most relevant chunks
• Answers (include_answer) written by Claude from the retrieved results
• Crawling and site maps with depth, breadth, limit and regex path/domain filters
• MCP server for Claude Code, Claude Desktop, Cursor and other MCP clients, over HTTP at /mcp or stdio with siftdog mcp
• SSRF protection: private and internal addresses are blocked, including via redirects and DNS rebinding
• MIT licensed

Use it as a drop-in Tavily replacement

Point the official Tavily clients at your Siftdog server with api_base_url. The key can be any string when auth is disabled, or one of your API_KEYS.

from tavily import TavilyClient

client = TavilyClient(api_key="your-siftdog-key", api_base_url="http://localhost:8000")
results = client.search("latest python release", search_depth="advanced", max_results=5)
pages = client.extract(urls=["https://en.wikipedia.org/wiki/Okapi_BM25"])

LangChain, through langchain-tavily:

from langchain_tavily import TavilySearch

search = TavilySearch(
    max_results=5, tavily_api_key="your-siftdog-key", api_base_url="http://localhost:8000"
)
search.invoke({"query": "what is BM25 ranking"})

Tested with tavily-python 0.8.4 (search, extract, crawl, map; sync and async) and langchain-tavily 0.2.18 (search, extract).

Quick start

Docker Compose (includes SearXNG)

The full stack, with a SearXNG instance for /search, using the published image:

git clone https://github.com/khsarvar/siftdog && cd siftdog
cp .env.example .env          # optional: set API_KEYS and ANTHROPIC_API_KEY
docker compose up

Try a search:

curl -s localhost:8000/search -H "Content-Type: application/json" \
  -d '{"query": "latest python release", "search_depth": "advanced"}'

If you set API_KEYS, add -H "Authorization: Bearer <key>". OpenAPI docs are served at http://localhost:8000/docs.

Docker image only

docker run -p 8000:8000 ghcr.io/khsarvar/siftdog

/extract, /crawl and /map work on their own. For /search, point it at a SearXNG instance with the JSON format enabled: -e SEARXNG_URL=http://your-searxng:8080. Images are published for linux/amd64 and linux/arm64, tagged latest and by version (0.1.0, 0.1).

pip

pip install siftdog
SEARXNG_URL=http://your-searxng:8080 siftdog --port 8000

Configuration is read from environment variables or a .env file (see Configuration).

Use with MCP clients (Claude, Cursor, ...)

Siftdog is also an MCP server with four read-only tools: siftdog_search, siftdog_extract, siftdog_crawl and siftdog_map.

Connect to a running Siftdog server (Streamable HTTP at /mcp). With Claude Code:

claude mcp add --transport http siftdog http://localhost:8000/mcp \
  --header "Authorization: Bearer <key>"      # omit the header if API_KEYS is empty

Or run it locally over stdio with uv, no server needed. SEARXNG_URL is only needed for siftdog_search:

claude mcp add siftdog -e SEARXNG_URL=http://your-searxng:8080 -- uvx siftdog mcp

Claude Desktop (claude_desktop_config.json), Cursor (.cursor/mcp.json) and most other clients take the same command as JSON:

{
  "mcpServers": {
    "siftdog": {
      "command": "uvx",
      "args": ["siftdog", "mcp"],
      "env": { "SEARXNG_URL": "http://your-searxng:8080" }
    }
  }
}

API keys work as for the REST API: send Authorization: Bearer <key>, or append ?api_key=<key> to the URL for clients that can't set headers (URLs can end up in logs, so prefer the header). The HTTP endpoint only answers requests addressed to localhost unless you list your hostname in MCP_ALLOWED_HOSTS.

Siftdog vs Tavily, Firecrawl and crw

Measured results: Siftdog vs Tavily search benchmark (reproducible with bench/).

When to pick something else: if you'd rather not run infrastructure, or you want Tavily's neural reranking, use hosted Tavily. If you need JavaScript-rendered pages or a scraping platform with more features, look at Firecrawl or crw. Siftdog is for teams that want the Tavily API on their own servers under a permissive license.

FAQ

What is Siftdog?

Siftdog is an open-source web search and extraction API for AI agents. It reproduces the Tavily API (/search, /extract, /crawl, /map) on infrastructure you run yourself, using SearXNG for search results, trafilatura for content extraction and BM25 for relevance ranking.

Is Siftdog a drop-in replacement for Tavily?

For the four core endpoints, yes. The request and response fields match Tavily's, and the official tavily-python SDK and langchain-tavily work by setting api_base_url. The differences: relevance scores come from BM25 rather than a neural reranker, instructions (crawl/map) and include_image_descriptions (search) are accepted but ignored, and Tavily's /research endpoint isn't implemented.

Do I need a search API key?

No. Search results come from SearXNG, which queries public search engines. The only optional key is ANTHROPIC_API_KEY, used when a request sets include_answer.

Does it work with LangChain?

Yes, through the official langchain-tavily package. Pass api_base_url pointing at your Siftdog server, as in the example above.

Does Siftdog have an MCP server?

Yes. The API server exposes MCP over Streamable HTTP at /mcp, and uvx siftdog mcp runs it over stdio for local clients such as Claude Desktop and Cursor. See Use with MCP clients.

Why does /search return 502 "failing engines"?

SearXNG gets its results by querying public search engines (Brave, DuckDuckGo, Google and others), and those engines rate-limit or CAPTCHA an IP that sends many searches. When every engine is failing, Siftdog returns 502 with the engines and reasons, for example failing engines: brave (Suspended: too many requests), duckduckgo (CAPTCHA), rather than an empty result list your agent would mistake for "nothing found". Engines recover on their own, from minutes to about a day. If some engines still work, you get their results and the server logs which engines were down. To reduce blocking, enable more engines in docker/searxng/settings.yml and avoid bursts of identical searches.

Is it safe to expose Siftdog on a public server?

Set API_KEYS so only your clients can call it. /extract and /crawl fetch caller-supplied URLs, so Siftdog refuses private, loopback and link-local addresses, checked on every redirect and at connect time against the exact address used, which also stops DNS rebinding.

Can I run it without Docker?

Yes: pip install siftdog, then run siftdog with SEARXNG_URL pointing at any SearXNG instance with the JSON output format enabled. /extract, /crawl and /map work without SearXNG.

Local development

python3 -m venv .venv && .venv/bin/pip install -e ".[dev]"
docker compose up searxng -d    # uncomment its `ports:` in docker-compose.yml first
.venv/bin/siftdog             # http://127.0.0.1:8000, docs at /docs
.venv/bin/pytest                # offline test suite
.venv/bin/ruff check . && .venv/bin/ruff format .

API

All endpoints take JSON POST bodies and a Authorization: Bearer <key> header (a legacy api_key body field is also accepted). If API_KEYS is empty, auth is disabled.

Differences from hosted Tavily: instructions (crawl/map) and include_image_descriptions are accepted but ignored; relevance scores come from BM25, not a neural reranker.

Configuration

Environment variables (see .env.example): API_KEYS, SEARXNG_URL, ANSWER_ENABLED, ANSWER_MODEL, ANSWER_EFFORT, FETCH_TIMEOUT, FETCH_CONCURRENCY, FETCH_MAX_BYTES, ALLOW_PRIVATE_NETWORKS, CRAWL_MAX_LIMIT, MCP_ALLOWED_HOSTS.

MCP_ALLOWED_HOSTS lists the hostnames the /mcp endpoint answers besides localhost, for example search.example.com,search.example.com:*. Requests addressed to any other host get 421, which protects a local server from DNS-rebinding attacks by web pages.

Security: /extract and /crawl make the server fetch caller-supplied URLs. Requests to private, loopback and link-local addresses are blocked (including via redirects) unless ALLOW_PRIVATE_NETWORKS=true. The check runs at connect time against the exact address being connected to, so DNS rebinding can't get around it. Fetches of user URLs ignore HTTP(S)_PROXY, since a proxy would hide the destination address. As defense in depth for hostile multi-tenant deployments, also restrict egress at the network level.

License

Siftdog is released under the MIT License. The "Siftdog" name is covered separately by the trademark policy: use the code freely, but forks and hosted services need a different name.