FieldCure MCP Essentials

Install once, get the basics. A Model Context Protocol (MCP) server that provides 20 essential tools — HTTP requests, web search & fetch, URL file downloads, Wolfram|Alpha computational knowledge, shell commands, JavaScript execution, file I/O, environment info, and persistent memory — for any MCP client. Category search (news, images, scholar, patents) and runtime engine switching (get/set) are always available; capabilities are guarded at invocation time against the active engine. Built with C# and the official MCP C# SDK.

Features

• 20 essential tools — HTTP, web search & fetch, URL file downloads, runtime search-engine switching (get/set), Wolfram|Alpha, shell, JavaScript sandbox, environment info, file read/write/search, persistent memory + category search (news, images, scholar, patents)
• Zero configuration — no API keys needed for default Bing search; optional API keys unlock Serper, Tavily, SerpApi (+ category search tools), and Wolfram|Alpha
• Document parsing — web_fetch and read_file extract text from PDF, DOCX, HWPX, PPTX, XLSX into Markdown. PDF text extraction is text-layer only; scanned PDFs without a text layer yield empty text. For OCR-backed indexing use fieldcure-mcp-rag.
• Sandboxed JavaScript — Jint engine with strict limits (timeout, statement count, recursion depth)
• SSRF protection — HTTP requests, web fetch, and file downloads block private IP ranges and loopback addresses
• Cross-client — works with Claude Desktop, VS Code, AssistStudio, and any MCP-compatible client
• Stdio transport — standard MCP subprocess model via JSON-RPC over stdin/stdout

Installation

dotnet tool install -g FieldCure.Mcp.Essentials

After installation, the fieldcure-mcp-essentials command is available globally.

From source

git clone https://github.com/fieldcure/fieldcure-mcp-essentials.git
cd fieldcure-mcp-essentials
dotnet build

Requirements

• .NET 8.0 Runtime or later

Tools

Category Search (SerpApi / Serper / Tavily)

Always registered. Each tool runtime-guards on the active engine's capabilities and returns a descriptive error pointing at set_search_engine when the current engine does not support the category.

Runtime engine switching

web_search vs web_fetch vs download_file vs http_request

Document Parsing

web_fetch and read_file can parse binary documents into Markdown:

Output includes headings, tables, math expressions ([math: LaTeX]), and slide/page separators.

File Downloads

download_file saves the original bytes from an HTTP(S) URL. If save_path is omitted, the tool infers a filename from Content-Disposition, the URL path, or a generated fallback name. Relative save_path values resolve under the configured download_directory; absolute paths are used as-is except for protected system directories.

The default download directory is ~/Downloads/mcp and is created automatically on first use. Downloads are written to a temporary file in the destination directory and then committed with an atomic move/replace, so failed or cancelled downloads do not leave a partial final file.

{
  "url": "https://example.com/report.pdf"
}

{
  "url": "https://example.com/report.pdf",
  "save_path": "reports/report.pdf",
  "overwrite": false
}

Web Search

Default engine is Bing (free, no API key needed). For more reliable results, use an API-based engine:

# Use Serper
fieldcure-mcp-essentials --search-engine serper --search-api-key YOUR_KEY

# Use Tavily
fieldcure-mcp-essentials --search-engine tavily --search-api-key YOUR_KEY

# Or via environment variables
ESSENTIALS_SEARCH_ENGINE=serper ESSENTIALS_SEARCH_API_KEY=xxx fieldcure-mcp-essentials

Environment Variable Auto-Detection

When --search-engine is omitted, the server scans environment variables and automatically selects the best available engine:

Detection priority: Serper → SerpApi → Tavily → Bing/DuckDuckGo fallback.

API Key Security

Region

Use the region parameter for localized results:

// Korean results
{ "query": "서울 맛집", "region": "ko-kr" }

// US English results
{ "query": "best restaurants NYC", "region": "en-us" }

// Global (default)
{ "query": "Python tutorial" }

Without --search-engine, a fallback engine (Bing → DuckDuckGo) auto-switches on CAPTCHA. Free engines rely on scraping and may be intermittent — an API-based engine is strongly recommended for any non-trivial use.

Explicit paid engine without a key — MCP Elicitation

When --search-engine serper|tavily|serpapi is selected explicitly but no API key is configured (CLI arg, ESSENTIALS_SEARCH_API_KEY, or engine-specific env var), the server waits until the first web_search call and then asks the MCP client for the key via MCP Elicitation. If the user declines, a follow-up prompt asks whether to run the search with free Bing/DuckDuckGo instead. Declining both lets the tool soft-fail with a clear message so the LLM can recover.