MCP Servers Overview
MCP (Model Context Protocol) is an open standard developed by Anthropic for connecting LLMs to external tool servers. It defines how an AI agent discovers and calls tools from any external system — turning any service into a set of agent-callable functions.
TARX implements MCP as a first-class feature: connect MCP servers to your project, assign them to agents, and your agents gain access to those tools at runtime.
What MCP Is
MCP is to LLM tools what USB is to peripherals — a standard plug that lets any device connect to any compatible host. Before MCP, every tool integration required custom code. With MCP:
- A server developer exposes their tools once via the MCP protocol
- Any MCP-compatible client (like TARX) can discover and use those tools automatically
- No custom code required on the client side
What an MCP Server Looks Like
An MCP server is a service that:
- Accepts an MCP handshake (initialize → tools/list)
- Returns a list of available tools with their schemas
- Executes tool calls when requested
From your agent's perspective, MCP tools appear exactly like built-in capabilities — the LLM calls them by name, TARX executes them and returns results.
Why MCP Matters for Agents
On its own, an agent has just two built-in capabilities (web_search, web_scraper). MCP is how you give agents real reach into external systems — GitHub, Jira, Slack, databases, CRMs, and dozens more:
| Without MCP | With MCP |
|---|---|
| 2 built-in capabilities | 2 + the tools of every connected MCP server |
Generic HTTP calls (the http_request node) | Native GitHub/Jira/Slack/etc. tool calls |
| Manual API integration in a system prompt | Auto-discovered tools with full schemas |
| You write the integration | The MCP server provides it |
TARX ships a curated catalog of 50 online MCP servers across 12 categories — every one is an online service (no local-instance servers). See the full list in the MCP Catalog.
Two Ways MCP Servers Are Hosted
When you add a server from the catalog, it uses one of two hosting models. Both feel identical once connected — the difference is only where the server runs.
| Hosting model | What it means | What you provide |
|---|---|---|
| Cloud / online MCP | The vendor runs a public MCP endpoint (e.g. GitHub, Notion, Stripe). TARX connects to it over HTTPS. | Just your credential (API key / token) |
| TARX-hosted MCP | TARX runs the MCP server for you on its gateway, so you don't host anything. | Just your credential (connection string / API key) |
There is also a Custom MCP option: paste the URL of any MCP server you run yourself or another provider exposes.
MCP Server Examples
| MCP Server | A few of its tools |
|---|---|
| GitHub | get_file_contents, create_pull_request, search_code, create_issue |
| Jira | create_issue, update_issue, search_issues, list_sprints |
| Slack | send_message, list_channels, search |
| Notion | search, create_page, query_database |
| PostgreSQL | query, list_tables, describe schema |
See all 50 servers and their categories in the MCP Catalog.
MCP Protocol Basics
At a technical level, MCP communication:
- Initialize: Client sends
initializerequest with capabilities - Tools list: Client sends
tools/list— server responds with all available tools + JSON schemas - Tool call: When LLM requests a tool call, client sends
tools/callwith tool name + arguments - Result: Server returns the tool execution result
TARX handles all protocol details. You configure the server URL and credentials; TARX manages the handshake, tool discovery, and call dispatching.
MCP Transport Types
MCP supports two transport types:
| Transport | When to Use |
|---|---|
| HTTP/SSE | Most cloud MCP servers — TARX connects via HTTPS |
| stdio | Local process MCP servers — TARX spawns the process (future feature) |
Currently, TARX supports HTTP-based MCP servers (the most common for cloud-hosted tools). stdio support for local MCP processes is on the roadmap.
Security Model
MCP server credentials are project-level credentials:
- Stored encrypted in TARX
- Only accessible to project admins (to add/delete MCP servers)
- Used by all project agents assigned that MCP server
- Never exposed via API responses
When an agent runs, TARX:
- Reads the MCP server config
- Decrypts credentials in-memory
- Connects to the MCP server with those credentials
- Runs the session
- Disconnects — credentials never persist in memory after the session
Next Steps
- Connecting MCP Servers — How to add servers to your project
- MCP in Agents — How discovered tools work at runtime