agent search mcp

Agent Search MCP: Free Web Search for AI Agents

A lightweight, free-first MCP web search router with compact multi-source evidence.

Agent Search MCP is an open-source, self-hosted MCP server and CLI. It starts without an API key, searches English and Chinese sources, keeps optional paid providers behind an explicit policy, and caps provider calls, search time, result count, and evidence size.

中文文档 · Benchmarks · Architecture · CHANGELOG

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Install

npx -y agent-search-mcp

Requires Node.js >= 18.17. The default runtime does not require a browser, database, Python, or a search API account.

Connect an MCP client

Use this stdio configuration in MCP clients that accept mcpServers JSON, including Claude Desktop, Cursor, VS Code, and Windsurf:

{
  "mcpServers": {
    "agent-search": {
      "command": "npx",
      "args": ["-y", "agent-search-mcp"]
    }
  }
}

Claude Code and Codex can register the same npx -y agent-search-mcp stdio command through their MCP settings.

After a global install, check the local runtime without making a search request:

npm install -g agent-search-mcp
fasm doctor

Why Agent Search MCP

Need	Product behavior
Free web search	Zero-key sources work without an API account
Provider cost control	Paid providers run only under an explicit routing policy
Token cost control	Compact output and one evidence budget bound response size
Multi-source evidence	Results retain provenance, relevance, provider-family count, and partial failures
Chinese web search	Sogou and Baidu handle Chinese queries without a translation layer
Lightweight self-hosting	Pure Node.js runtime with stdio, Streamable HTTP, and CLI access

The default free_first policy never spends a configured API credential. free_only blocks paid providers. quality_escalation can call one configured paid provider after free evidence misses the quality gate, while paid_first tries that provider before the free fallback.

Request budgets cap adapter attempts, elapsed time, and admitted results. The evidence budget caps query-relevant passages across the complete response. Compact mode keeps full detail for the first results and reduces later entries to source-preserving references.

Measured token reduction

The checked-in bilingual fixture measures formatting with a locked tokenizer:

Output	Average tokens per query	Savings vs normal
Normal	2311.0
Compact	1655.8	28.4%
Compact+	1607.5	30.4%

This fixture verifies output formatting and evidence-packet behavior. It does not measure live engine availability or search quality. See the benchmark method and limitations.

How the search router works

flowchart LR
    A["AI agent"] --> M["MCP search tools"]
    M --> P["Provider and request policy"]
    P --> F["Zero-key sources"]
    P --> O["Optional paid provider"]
    F --> E["Deduplicate, rank, and preserve failures"]
    O --> E
    E --> B["Evidence and token budget"]
    B --> R["Compact multi-source result"]

The router evaluates each search batch against separate result, relevance, confidence, and provider-family gates. It stops after the evidence passes those gates and exposes the decision in meta.execution. Provider failures stay visible in partialFailures, so an empty result cannot hide an upstream error.

The source-level product comparison explains where Agent Search MCP differs from Tavily, Exa, Brave Search, Firecrawl, and MCP Web Hound. It compares routing, evidence, local operation, paid-provider boundaries, and Chinese search without volatile pricing or popularity claims.

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Engines

The runtime registers 16 adapters: 9 zero-key adapters and 7 optional API adapters.

Engine	Access	Languages	Role
DuckDuckGo	Zero-key	en	General Web Search
Sogou Search	Zero-key	zh	Chinese Web Search
Bing	Zero-key	en, zh	Multilingual Web Search
Baidu	Zero-key	zh	Chinese Web Search
Wikipedia	Zero-key	en, zh, ja, de, fr, es, auto	Encyclopedic references
Startpage	Zero-key	en, auto	Privacy-oriented Web Search
Yandex	Zero-key	ru, en, auto	Russian and international Web Search
Mojeek	Zero-key	en, auto	Independent privacy-oriented index
Wiby	Zero-key	en	Independent small-Web index
Brave Search	BRAVE_API_KEY	en, zh	Optional commercial Web Search
Tavily Search	TAVILY_API_KEY	en, zh	Optional agent-oriented Search
Exa Search	EXA_API_KEY	en, zh	Optional neural Search
You.com Search	YDC_API_KEY	en, zh	Optional commercial Web Search
Tencent Web Search API	TENCENT_WSA_API_KEY	zh	Optional official Chinese Web Search
Bocha Web Search	BOCHA_API_KEY	zh, en	Optional Chinese-first AI Search
Serper Google Search	SERPER_API_KEY	en, zh, auto	Optional Google SERP Search

Tools

Tool	Description	Best for
free_search	Multi-engine Web Search with bounded fallback	Quick facts and general discovery
free_search_advanced	Filtered waterfall search and optional enrichment	Domain policy and progressive verification
free_extract	Extract a URL as clean Markdown	Reading complete source pages
fetch_github_readme	Fetch a public GitHub repository README	Project documentation
fetch_csdn_article	Fetch a CSDN article	Chinese technical articles
fetch_juejin_article	Fetch a Juejin article	Chinese developer articles
search_with_synthesis	Search evidence with an LLM synthesis hint	Agent-authored answers from cited evidence

Capability controls

Environment	Default	Purpose
ENABLED_TOOLS / DISABLED_TOOLS	all / none	Tool registration allowlist and denylist; deny wins
ALLOWED_ENGINES / DENIED_ENGINES	all / none	Engine execution allowlist and denylist; deny wins
SEARCH_PROVIDER_MODE	free_first	Default routing: free_first, quality_escalation, paid_first, or free_only
PAID_ENGINE_ORDER	brave,exa,tavily,youcom,tencent_wsa,bocha,serper	Selects the first configured optional provider; not a quality claim
SEARCH_BUDGET_MAX_CALLS	16	Adapter-attempt budget
SEARCH_BUDGET_MAX_ELAPSED_MS	30000	End-to-end elapsed-time budget
SEARCH_BUDGET_MAX_RESULTS	100	Admitted raw-result budget
EVIDENCE_BUDGET_CHARS	1200	Evidence-character budget

Wiby is a genuine zero-key source backed by its official JSON API and is used late in the free waterfall as an independent small-Web supplement. Optional providers require user credentials; any signup credit or trial quota is provider-controlled and is not treated as permanent free access.

All tools are read-only and idempotent. Search cancellation reaches rate-limit waits, retries, provider requests, and optional enrichment. Enrichment can improve a snippet but cannot increase source confidence or independent source count.

free_search_advanced.time_range remains in the compatibility schema. The server returns UNSUPPORTED_FILTER before searching because the general web providers do not share one enforceable recency contract.

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Configuration

The generated capability table above lists the default request budgets. These settings cover the common deployment choices:

Goal	Environment variables
Add an optional provider	BRAVE_API_KEY, TAVILY_API_KEY, EXA_API_KEY, YDC_API_KEY, TENCENT_WSA_API_KEY, BOCHA_API_KEY, or SERPER_API_KEY
Choose spend policy	SEARCH_PROVIDER_MODE, PAID_ENGINE_ORDER
Reduce response tokens	OUTPUT_STYLE=compact, MAX_FULL_RESULTS, SNIPPET_LENGTH, EVIDENCE_BUDGET_CHARS
Restrict tools or engines	ENABLED_TOOLS, DISABLED_TOOLS, ALLOWED_ENGINES, DENIED_ENGINES
Use an explicit proxy	DUCKDUCKGO_PROXY_URL, SOGOU_PROXY_URL, or USE_PROXY=true with PROXY_URL
Persist the exact-result cache	SEARCH_CACHE_DIRECTORY, SEARCH_CACHE_TTL_MS, SEARCH_CACHE_MAX_ENTRIES
Enable optional semantic processing	SEMANTIC_DEDUP, SEMANTIC_RERANK, DEDUP_THRESHOLD, RERANK_TOP_K

Adding an API key does not authorize paid traffic. The routing policy controls provider use. The default exact-result cache stays in memory; setting SEARCH_CACHE_DIRECTORY opts into local persistence. Semantic processing is the only optional feature that uses Python and Model2Vec.

HTTP deployment

HTTP mode requires HTTP_AUTH_TOKEN unless you set HTTP_ALLOW_UNAUTHENTICATED=true. Browser requests with an Origin header must match ALLOWED_ORIGINS. See the HTTP deployment guide for TLS termination, token rotation, and reverse-proxy examples.

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CLI

The package includes the fasm CLI:

fasm search "TypeScript MCP server"
fasm search "query" --count 5 --engines bing,baidu,youcom --json
fasm extract "https://example.com"
fasm extract "https://example.com" --json
fasm doctor
fasm doctor --json
HTTP_AUTH_TOKEN=change-me MODE=http npx agent-search-mcp

fasm doctor reads local configuration without network probes and never prints credential or proxy values.

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Documentation and evidence

Document	Contents
System architecture	Routing, evidence, provider families, and configuration
Product comparison	Source-level review of Agent search products
Benchmarks	Token fixture, live-run scope, and quality evaluation method
v3.2.0 release notes	Provider policy, budgets, and migration notes
Earlier release candidate evidence	Pre-expansion packed-install matrix and limitations
MCP 2026 readiness	Isolated protocol experiment and remaining gates

Companion: Slim Guard

Agent Search controls retrieval work and compresses search evidence. mcp-slim-guard sits between an agent and MCP servers to handle tool-schema compression and security policy.

npm install -g mcp-slim-guard

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Development

git clone https://github.com/lennney/agent-search-mcp.git
cd agent-search-mcp
npm install
npm run build
npm test
npm run dev        # stdio mode
npm run dev:http   # HTTP mode (port 3000)

The stable package supports Node.js 18, 20, and 22. The isolated MCP 2026 experiment requires Node.js 20 or newer.

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License

Apache 2.0

Based on open-websearch by Aas-ee.

If Agent Search MCP helps your agent, star the repository so other developers can find the project.