What is duckduckgo-mcp-server CLAUDE.md?

A project instruction file for duckduckgo-mcp-server, a local Python server that provides DuckDuckGo web search and webpage fetching to an AI coding assistant. It documents setup, commands, architecture, and tests.

Use it when developing or maintaining the server, running its unit or end-to-end tests, starting the MCP Inspector, or building the Python package.

It gives the coding assistant the repository-specific information needed to install, run, test, and build the server correctly.

How LLLeoLi/duckduckgo-mcp-server configures Claude Code

Reuse

Borrowing it

Nothing to install: this file belongs to LLLeoLi/duckduckgo-mcp-server. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file

curl -O https://raw.githubusercontent.com/LLLeoLi/duckduckgo-mcp-server/main/CLAUDE.md

Clone the repo

git clone --depth 1 https://github.com/LLLeoLi/duckduckgo-mcp-server

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/instructions/llleoli/duckduckgo-mcp-server/claude-md/github.svg)](https://agentmods.dev/instructions/llleoli/duckduckgo-mcp-server/claude-md)

Your own site

<a href="https://agentmods.dev/instructions/llleoli/duckduckgo-mcp-server/claude-md"><img src="https://agentmods.dev/badge/instructions/llleoli/duckduckgo-mcp-server/claude-md/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/instructions/llleoli/duckduckgo-mcp-server/claude-md"><img src="https://agentmods.dev/badge/instructions/llleoli/duckduckgo-mcp-server/claude-md.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 876 This file is loaded in full into every session.

When invoked 876 The same file — it is already loaded in full.

Security scan A 1 finding. A grade says what 26 rules found in the file — not that it is safe.

Origin original No closer match found in the catalogue.

Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

Model	Per session	Once invoked
Fable 5.1	$0.00876	$0.00876
Opus 5	$0.00438	$0.00438
Sonnet 5	$0.00175	$0.00175
Haiku 4.5	$0.00088	$0.00088

Measured 9d ago against content hash 17d7ad92f8d3, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade A, and why

duckduckgo-mcp-server CLAUDE.md scanned grade A with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 9d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

- `DDG_SEARCH_BACKEND`: `auto` (default) | `httpx` | `curl` — HTTP backend for the search tool. `auto` falls back to curl_cffi Chrome TLS impersonation when DuckDuckGo returns a fingerprint block (HTTP 202/403); `curl`/f

CLAUDE.md · 70 lines

How it starts

The opening of the file, as written. The whole thing — 70 lines — stays where its author put it; the contents beside it link to each section on GitHub.

CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

Project Overview

A Model Context Protocol (MCP) server providing DuckDuckGo web search and webpage content fetching. Built with Python using the FastMCP framework. Published to PyPI as duckduckgo-mcp-server.

Commands

# Install dependencies
uv sync

# Run the server
uv run duckduckgo-mcp-server

# Run with MCP Inspector (for interactive testing)
mcp dev src/duckduckgo_mcp_server/server.py

# Run all tests (unit + e2e)
uv run python -m pytest src/duckduckgo_mcp_server/ -v

# Run only unit tests
uv run python -m pytest src/duckduckgo_mcp_server/test_server.py -v

# Run only e2e MCP protocol tests
uv run python -m pytest src/duckduckgo_mcp_server/test_e2e.py -v

# Run a single test
uv run python -m pytest src/duckduckgo_mcp_server/test_server.py::TestRateLimiter::test_acquire_removes_expired_entries

# Build package
uv build

Architecture

Single-module server in src/duckduckgo_mcp_server/server.py with three main classes:

DuckDuckGoSearcher — Scrapes DuckDuckGo's HTML endpoint (html.duckduckgo.com/html) via POST requests. Parses results with BeautifulSoup. Handles SafeSearch (kp param) and region (kl param) configuration.
WebContentFetcher — Fetches arbitrary URLs, strips non-content elements (script, style, nav, header, footer), and returns cleaned text truncated to 8000 chars.
RateLimiter — Sliding-window rate limiter (30 req/min for search, 20 req/min for content fetching).

Two MCP tools are exposed: search and fetch_content.

Configuration

Environment variables read at startup (not per-request):

DDG_SAFE_SEARCH: STRICT | MODERATE (default) | OFF
DDG_REGION: Region code like us-en, cn-zh, jp-ja, wt-wt
DDG_ALLOW_PRIVATE_URLS: 1/true to let fetch_content reach loopback/private/link-local/metadata addresses (default off — SSRF guard). Also settable via --allow-private-urls.
DDG_SEARCH_BACKEND: auto (default) | httpx | curl — HTTP backend for the search tool. auto falls back to curl_cffi Chrome TLS impersonation when DuckDuckGo returns a fingerprint block (HTTP 202/403); curl/fallback need the [browser] extra. Also settable via --search-backend.

Read the full file on GitHub · 70 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

9d ago First seen · 70 lines · 876 tokens per session scan A 17d7ad92f8d3

Subscribe to this mod's changes

duckduckgo-mcp-server CLAUDE.md is an instructions file published in the GitHub repository LLLeoLi/duckduckgo-mcp-server (0 stars, last pushed 29d ago), licensed MIT. It adds 876 tokens to every session, about $0.0044 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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duckduckgo-mcp-server: Instructions file for Claude Code