Reasonix: Open-Source Coding Agent for DeepSeek, Setup and MCP Servers

1. 1

   Install Reasonix and pick a model

   Install it with the command in the box above, then run reasonix setup. Add the DeepSeek provider (or any OpenAI- or Anthropic-compatible one), paste your key, choose a default model and pick Save and exit.

   The key is saved in ~/.reasonix/.env. Reasonix does not read a DEEPSEEK_API_KEY exported in your shell, so enter it here.

   Tip: Get a DeepSeek key at platform.deepseek.com/api_keys.

2. 2

   Add a local server from the terminal

   reasonix mcp add fs -- npx -y @modelcontextprotocol/server-filesystem .

   Everything after -- is the launch command. Use --env K=V to pass a setting to the server. The entry is saved to ~/.reasonix/config.toml.

   Tip: CLI changes apply on the next session. In a running session, open /mcp and press n to add and connect now.

3. 3

   Add a hosted server with a key

   reasonix mcp add stripe --http https://mcp.stripe.com --header "Authorization=Bearer $STRIPE_KEY"

   Use --sse <url> instead of --http for an older SSE server. Servers that sign you in through your browser need no header; see the sign-in step below.

   Uses Stripe MCP

4. 4

   Or edit the config file by hand

   Servers you install live in ~/.reasonix/config.toml (Windows: %APPDATA%\reasonix\config.toml). Servers for one project go in reasonix.toml in the project root, and they override global entries with the same name.

   [[plugins]]                       # local server
   name    = "example"
   command = "reasonix-plugin-example"
   # startup_timeout_seconds = 60    # optional
   # call_timeout_seconds = 600       # optional
   
   [[plugins]]                       # hosted server over Streamable HTTP
   name    = "stripe"
   type    = "http"
   url     = "https://mcp.stripe.com"
   headers = { Authorization = "Bearer ${STRIPE_KEY}" }

   ${STRIPE_KEY} expands from your environment, so the key stays out of the file.

5. 5

   Or reuse a .mcp.json

   Reasonix reads a Claude-style .mcp.json in the project root as it is. If the same name appears in reasonix.toml, the TOML entry wins.

   {
     "mcpServers": {
       "filesystem": { "command": "npx", "args": ["-y", "@modelcontextprotocol/server-filesystem", "/path"] },
       "stripe": { "type": "http", "url": "https://mcp.stripe.com", "headers": { "Authorization": "Bearer ${STRIPE_KEY}" } }
     }
   }

6. 6

   Start a session and check the server

   Run cd your-project, then reasonix. Answer the Trust this folder prompt, and servers connect in the background.

   Type /mcp to see each server and its tools. Press r to reconnect a failed one.

   Tip: A server gets 30 seconds to start by default. Raise startup_timeout_seconds in its entry if it needs longer.

7. 7

   Sign in to a hosted server if it asks

   Press a in the /mcp panel, or run reasonix mcp auth <name> in your shell. Reasonix handles the sign-in details itself.

   To browse the official MCP Registry instead, run reasonix mcp browse and then reasonix mcp install <registry-name>.

8. 8

   Use it by name

   Ask in plain words. Reasonix shows each tool to the model as mcp__<server>__<tool>.

   PromptCopy

   Use the fs server to list the files in this folder and tell me which one is largest.

   Tip: Calls time out after 300 seconds by default.

9. 9

   Hide tools you do not want

   Add disabled_tools to the server's entry to hide tools by their exact name.

   disabled_tools = ["write_file", "delete_file"]

   Installing a server authorizes all its tools to run without asking each time, so this is the way to keep a server read-only.

1. 1
   Stripe MCPOfficialHosted or LocalOAuth

   Reasonix's own guide and command help use Stripe's hosted server as the example of a remote server with a key.

   2,014 GitHub stars
2. 2
   Context7OfficialHosted or LocalAPI key

   Looks up current library docs. A Reasonix user reports it connects normally when started with npx.

   64,001 GitHub stars
3. 3
   Playwright MCPOfficialLocal

   Drives a real browser to test what Reasonix builds. The same user report lists it as working.

   38,887 GitHub stars
4. 4
   GitHub MCP ServerOfficialHosted or LocalOAuth

   Pull requests, issues and code search. A startup bug with it was fixed in Studio 2.20.0, and a later user says their config works.

   34,115 GitHub stars

Reasonix is a good pick for a free, open-source agent on DeepSeek or another cheap model, with MCP set up in one command. The main limit is that installed servers run all their tools without asking, and it has had many security fixes, so stay on 2.53.0 or later.