MCP configuration schema

When mistral.rs acts as an MCP client (see connect to MCP server), it reads a JSON config describing servers to connect to.

Top-level fields

{
  "servers": [ ... ],
  "auto_register_tools": true,
  "tool_timeout_secs": 30,
  "max_concurrent_calls": 10
}

Field	Type	Default	Purpose
servers	array	required	List of MCP servers.
auto_register_tools	bool	true	Expose every tool from every connected server to the model.
tool_timeout_secs	int	30	Per-tool-call timeout.
max_concurrent_calls	int	10	Cap on concurrent MCP calls.

Server entry

{
  "name": "filesystem",
  "source": { ... },
  "enabled": true,
  "tool_prefix": "fs",
  "bearer_token": "..."
}

Field	Type	Required	Purpose
id	string	no (auto UUID)	Stable identifier for the server.
name	string	yes	Server name.
source	object	yes	Transport configuration.
enabled	bool	no (default true)	Disable a server without removing the entry.
tool_prefix	string	no (auto-generated mcp_<uuid>)	Prefix applied to tool names.
resources	array	no	Optional resource list.
bearer_token	string	no	Optional bearer token.

Transports, source object

Process (stdio)

{
  "type": "Process",
  "command": "npx",
  "args": ["-y", "@modelcontextprotocol/server-filesystem", "/tmp"],
  "env": { "KEY": "value" },
  "work_dir": "/path"
}

Field	Purpose
type	Literal "Process".
command	Executable to run.
args	Arguments.
env	Optional environment variables.
work_dir	Optional working directory.

HTTP

{
  "type": "Http",
  "url": "https://mcp.example.com",
  "headers": { "Authorization": "Bearer ..." },
  "timeout_secs": 60
}

Field	Purpose
type	Literal "Http".
url	Endpoint URL.
headers	Optional request headers.
timeout_secs	Optional per-source timeout.

WebSocket

{
  "type": "WebSocket",
  "url": "wss://mcp.example.com/ws",
  "headers": { ... },
  "timeout_secs": 60
}

Same fields as HTTP with a WebSocket URL.

Tool name prefix

Tools from a server with tool_prefix = "fs" are exposed as fs_read_file, fs_list_directory, etc. The separator is an underscore. Without tool_prefix, an auto-generated mcp_<uuid> prefix is used.

Example

{
  "servers": [
    {
      "name": "filesystem",
      "tool_prefix": "fs",
      "source": {
        "type": "Process",
        "command": "npx",
        "args": ["-y", "@modelcontextprotocol/server-filesystem", "/srv/agent-workspace"]
      }
    },
    {
      "name": "github",
      "source": {
        "type": "Http",
        "url": "https://mcp.github.example.com",
        "headers": {
          "Authorization": "Bearer xxx"
        }
      }
    }
  ],
  "auto_register_tools": true,
  "max_concurrent_calls": 8,
  "tool_timeout_secs": 45
}

Pass it on the CLI:

mistralrs serve --mcp-config mcp.json -m Qwen/Qwen3-4B

The same path can be supplied via the MCP_CONFIG_PATH environment variable.