Module: Reeve::Integrations::FastMcp::ContextBuilder

Defined in:
lib/reeve/integrations/fast_mcp/context_builder.rb

Overview

Turns what a fast-mcp tool instance knows about its request into the attributes a Reeve::Context is built from.

fast-mcp constructs a tool as tool.new(headers: headers) per request and calls call_with_schema_validation! on it, so the transport's headers are the only per-request context a tool has. They are passed through to the principal resolver untouched: the header that identifies the human is the host's decision, not ours (research R2, resolved against fast-mcp 1.6.0).

Constant Summary collapse

AGENT_HEADERS =

Checked in order. The first that answers names the client for attribution only.

%w[X-MCP-Client X-Client-Name User-Agent].freeze

Class Method Summary collapse

Class Method Details

.agent_id(headers) ⇒ Object

Attribution is not authorization: a client that names itself is recorded by that name, and one that does not is recorded as unknown rather than refused.



37
38
39
40
41
42
43
44
 
# File 'lib/reeve/integrations/fast_mcp/context_builder.rb', line 37

def agent_id(headers)
  AGENT_HEADERS.each do |header|
    value = headers[header] || headers[header.downcase]
    return value.to_s unless value.nil? || value.to_s.strip.empty?
  end

  Context::UNKNOWN_AGENT_ID
end

.attributes(tool) ⇒ Object 



21
22
23
24
25
26
27
28
 
# File 'lib/reeve/integrations/fast_mcp/context_builder.rb', line 21

def attributes(tool)
  headers = headers_for(tool)

  {
    agent: { id: agent_id(headers), name: headers["X-MCP-Client"] },
    metadata: { headers: headers }
  }
end

.headers_for(tool) ⇒ Object 



30
31
32
33
 
# File 'lib/reeve/integrations/fast_mcp/context_builder.rb', line 30

def headers_for(tool)
  headers = tool.respond_to?(:headers) ? tool.headers : nil
  headers.is_a?(Hash) ? headers : {}
end