docs(tools): add DuckDuckGo Search provider page

New page: tools/duckduckgo-search.md
- Key-free fallback provider, no API key needed
- Clear Warning about unofficial HTML-based integration
- Limitations section covering bot-challenge risk and reliability
- CardGroup showing good-for vs not-recommended-for use cases

Updated: tools/web.md with DuckDuckGo in CardGroup and comparison table
Updated: docs.json nav and redirect

docs/docs.json

@@ -88,6 +88,10 @@
       "source": "/web-fetch",
       "destination": "/tools/web-fetch"
     },
+    {
+      "source": "/duckduckgo-search",
+      "destination": "/tools/duckduckgo-search"
+    },
     {
       "source": "/gemini-search",
       "destination": "/tools/gemini-search"
@@ -1122,6 +1126,7 @@
                       "tools/web-fetch",
                       "tools/web",
                       "tools/brave-search",
+                      "tools/duckduckgo-search",
                       "tools/firecrawl",
                       "tools/gemini-search",
                       "tools/grok-search",

docs/tools/duckduckgo-search.md

@@ -0,0 +1,117 @@
+---
+summary: "DuckDuckGo web search -- key-free fallback provider (unofficial, HTML-based)"
+read_when:
+  - You want a web search provider that requires no API key
+  - You want to use DuckDuckGo for web_search
+  - You need a zero-config search fallback
+title: "DuckDuckGo Search"
+---
+
+# DuckDuckGo Search
+
+OpenClaw supports DuckDuckGo as a **key-free** `web_search` provider. No API
+key or account is required.
+
+<Warning>
+  DuckDuckGo is an **unofficial, HTML-based** integration. It scrapes
+  DuckDuckGo's non-JavaScript search pages, not an official API or SDK.
+  Expect occasional breakage from bot-challenge pages or HTML changes.
+  Use it as a convenient fallback, not a production-grade provider.
+</Warning>
+
+## Quick start
+
+DuckDuckGo requires no API key. Just set it as your provider:
+
+```bash
+openclaw configure --section web
+# Select "duckduckgo" as the provider
+```
+
+Or set the provider directly in config:
+
+```json5
+{
+  tools: {
+    web: {
+      search: {
+        provider: "duckduckgo",
+      },
+    },
+  },
+}
+```
+
+That's it — no keys, no plugin config, no environment variables.
+
+## How it works
+
+Unlike API-backed providers (Brave, Perplexity, Tavily), DuckDuckGo search
+works by:
+
+1. Sending an HTTP request to DuckDuckGo's non-JavaScript search endpoint
+2. Parsing the HTML response to extract search results
+3. Returning structured results with titles, URLs, and snippets
+
+This approach means:
+
+- **No API key needed** — works out of the box
+- **No rate limits from an API plan** — but DuckDuckGo may serve bot-challenge
+  pages under heavy use
+- **Results may differ** from what you see in DuckDuckGo's full web interface
+
+## Config
+
+```json5
+{
+  tools: {
+    web: {
+      search: {
+        enabled: true,
+        provider: "duckduckgo",
+      },
+    },
+  },
+}
+```
+
+No `plugins.entries` config is needed — DuckDuckGo has no API key or plugin-specific settings.
+
+## Supported parameters
+
+DuckDuckGo search supports the standard `query` and `count` parameters.
+Provider-specific filters like `country`, `language`, `freshness`, and
+`domain_filter` are not supported.
+
+## Limitations
+
+- **Unofficial integration** — not backed by a DuckDuckGo API or SDK
+- **Bot-challenge risk** — DuckDuckGo may serve CAPTCHAs or block requests
+  under heavy or automated use
+- **HTML parsing** — results depend on DuckDuckGo's page structure, which can
+  change without notice
+- **No advanced filters** — only `query` and `count` are supported
+- **Best-effort reliability** — treat this as a fallback, not a primary
+  provider for production use
+
+## When to use DuckDuckGo
+
+<CardGroup cols={2}>
+  <Card title="Good for" icon="check">
+    Quick local development, demos, testing, or environments where no API key
+    is available
+  </Card>
+  <Card title="Not recommended for" icon="x">
+    Production gateways, high-volume search, or workflows requiring reliable
+    uptime
+  </Card>
+</CardGroup>
+
+For production use, consider [Brave Search](/tools/brave-search) (free tier
+available) or another API-backed provider.
+
+## Related
+
+- [Web Search overview](/tools/web) -- all providers and auto-detection
+- [Brave Search](/tools/brave-search) -- structured results with free tier
+- [Gemini Search](/tools/gemini-search) -- AI-synthesized answers (also no search-specific key if you have a Gemini key)

docs/tools/web.md

@@ -49,6 +49,9 @@ returns results. Results are cached by query for 15 minutes (configurable).
   <Card title="Brave Search" icon="shield" href="/tools/brave-search">
     Structured results with snippets. Supports `llm-context` mode, country/language filters. Free tier available.
   </Card>
+  <Card title="DuckDuckGo" icon="bird" href="/tools/duckduckgo-search">
+    Key-free fallback. No API key needed. Unofficial HTML-based integration.
+  </Card>
   <Card title="Firecrawl" icon="flame" href="/tools/firecrawl">
     Structured results. Best paired with `firecrawl_search` and `firecrawl_scrape` for deep extraction.
   </Card>
@@ -74,6 +77,7 @@ returns results. Results are cached by query for 15 minutes (configurable).
 | Provider                               | Result style               | Filters                                          | API key                                     |
 | -------------------------------------- | -------------------------- | ------------------------------------------------ | ------------------------------------------- |
 | [Brave](/tools/brave-search)           | Structured snippets        | Country, language, time, `llm-context` mode      | `BRAVE_API_KEY`                             |
+| [DuckDuckGo](/tools/duckduckgo-search) | Structured snippets        | --                                               | None (key-free)                             |
 | [Firecrawl](/tools/firecrawl)          | Structured snippets        | Via `firecrawl_search` tool                      | `FIRECRAWL_API_KEY`                         |
 | [Gemini](/tools/gemini-search)         | AI-synthesized + citations | --                                               | `GEMINI_API_KEY`                            |
 | [Grok](/tools/grok-search)             | AI-synthesized + citations | --                                               | `XAI_API_KEY`                               |