Essentials

What essentials MCP server does

The essentials MCP server provides a broad collection of tools for research, computation, local automation, and persistent context. Its capabilities include raw HTTP requests, web search, page and document retrieval, file downloads, shell commands, sandboxed JavaScript, Wolfram|Alpha calculations, system information, file operations, and memory stored in SQLite.

Search tools cover general web results as well as recent news, images, academic papers, and patents. Category searches depend on the active search engine. The server can switch between Bing, DuckDuckGo, Serper, Tavily, and SerpApi at runtime, then report the selected engine and its supported categories.

How it works

The essentials MCP server uses the standard stdio transport. An MCP client starts the fieldcure-mcp-essentials process and communicates with it using JSON-RPC over standard input and output. The project is built with C# and the official MCP C# SDK.

Web retrieval tools serve different purposes. http_request returns raw HTTP responses for API calls and other requests. web_search returns result snippets, while web_fetch converts HTML pages and supported documents into Markdown. download_file preserves the original bytes on disk and supports a 100 MB limit.

web_fetch and read_file can parse PDF, DOCX, HWPX, PPTX, and XLSX files into Markdown. PDF extraction reads the text layer only, so scanned PDFs without embedded text do not produce OCR content. HTTP requests, web fetches, and downloads block private IP ranges and loopback addresses.

Setup and configuration

Install the global .NET tool with:

dotnet tool install -g FieldCure.Mcp.Essentials

The server requires .NET 8.0 or later. After installation, the fieldcure-mcp-essentials command is available to configure in an MCP client. Building from source requires cloning the repository and running dotnet build.

Bing is the default search engine and does not require an API key. The server can also use Serper, SerpApi, or Tavily. Set ESSENTIALS_SEARCH_ENGINE and ESSENTIALS_SEARCH_API_KEY, pass the equivalent command-line options, or let the server detect keys from SERPER_API_KEY, SERPAPI_API_KEY, and TAVILY_API_KEY. Paid-engine credentials are resolved when needed for a search.

Tools and capabilities

The essentials MCP server exposes tools for:

• Sending GET, POST, PUT, DELETE, PATCH, and HEAD requests with headers and bodies.
• Searching the web, news, images, scholarly papers, and patents.
• Fetching web content, downloading files, and parsing supported office documents.
• Running shell commands with a working directory, environment variables, shell choice, and output limits.
• Executing JavaScript in Jint with timeout, statement-count, and recursion limits.
• Querying Wolfram|Alpha for symbolic mathematics, plots, unit conversions, and constants.
• Reading, writing, appending, and searching local files.
• Inspecting local time, timezone, OS, hostname, username, and .NET version.
• Storing, deleting, and searching persistent key-value memories with SQLite and FTS5.

Limitations and notes

The essentials MCP server includes tools that can modify the local system, including shell execution, file writing, downloads, and memory deletion. Review tool arguments and client permissions before allowing agent use.

Relative download paths resolve beneath the configured download directory, which defaults to ~/Downloads/mcp; absolute paths are allowed except for protected system directories. Downloads use a temporary file followed by an atomic move, reducing the chance of leaving a partial destination file.

Category search tools remain registered even when the selected engine does not support them, but invocation returns an error explaining that another engine must be selected. Serper, SerpApi, and Tavily support different category sets, and Bing and DuckDuckGo do not provide the listed category searches. Wolfram|Alpha is optional and requires its configured service access.