class Riffer::Mcp::Client

Thin wrapper around the MCP Ruby SDK client (mcp gem v0.8+).

Resolves headers (if a Proc) once at initialization, then provides tools_list and tools_call. Used for discovery (+Manifest#discovery_headers+) and for tools/call when no credentials proc is configured.

MCP gem API used:

MCP::Client::HTTP.new(url:, headers:)  — HTTP transport (requires faraday)
MCP::Client.new(transport:)            — client
client.tools                           — Array<MCP::Client::Tool>
client.call_tool(tool:, arguments:)    — raw JSON-RPC response Hash

Public Class Methods

new (endpoint:, headers: {}, client: nil)

Source

# File lib/riffer/mcp/client.rb, line 21
def initialize(endpoint:, headers: {}, client: nil)
  depends_on "mcp"
  depends_on "faraday"

  @client = client || begin
    resolved_headers = Riffer::Helpers::CallOrValue.resolve(headers)
    transport = MCP::Client::HTTP.new(url: endpoint, headers: resolved_headers)
    MCP::Client.new(transport: transport)
  end
end

Public Instance Methods

tools_call (name, arguments = {})

Source

# File lib/riffer/mcp/client.rb, line 51
def tools_call(name, arguments = {})
  tool = MCP::Client::Tool.new(name: name, description: nil, input_schema: nil)
  response = @client.call_tool(tool: tool, arguments: arguments)

  if response["error"]
    raise Riffer::Error, response.dig("error", "message") || "MCP tool call failed"
  end

  if response.dig("result", "isError")
    message = (response.dig("result", "content") || []).filter_map { |item| item["text"] }.join
    raise Riffer::Error, message.empty? ? "MCP tool '#{name}' failed" : message
  end

  content = response.dig("result", "content") || []
  content.filter_map { |item| item["text"] }.join
end

Calls a tool on the MCP server and returns joined text content from the response.

tools_list ()

Source

# File lib/riffer/mcp/client.rb, line 37
def tools_list
  @client.tools.map do |tool|
    {
      name: tool.name,
      description: tool.description,
      input_schema: tool.input_schema
    }
  end
end

Returns an array of tool definition hashes, each with :name, :description, and :input_schema keys.