[3.13] AI Gateway: Document cookie-to-tool conversion for AI MCP Proxy plugin

[tomek-labuk]

Description

Add documentation explaining how the AI MCP Proxy plugin can take cookies from incoming HTTP requests and make them available as input parameters to tools. This allows browser-originated sessions and identities to flow through to MCP tools when needed (for example, when tools need session context or user identity). Major points to convey:

• Cookies in the request can be passed through to tools
• Tools can then use those values for context, auth, or other logic
• This enables browser-based workflows with MCP tools

Context: https://github.com/Kong/kong-ee/pull/12733/files#diff-ac66ce8fca7a2631a133688126685f85d63853077ff467cdf80bb8c5888d87db

NOTE: details TBD with Zexuan.

parameters:
- name: session_id
  in: cookie
  description: "Session identifier set by the authentication service. Treated as the proof of an authenticated session."
  required: true
  schema:
    type: string

Definition of Done [TBD]

• New section in the AI MCP Proxy plugin documentation describing cookie pass-through behavior
• At least one configuration example in the AI MCP Proxy Plugin showing cookies being surfaced to a tool
• Nice-to-have: how-to document

Additional information

Person of contact @spacewander
Jira ticket: https://konghq.atlassian.net/browse/AG-377

Size

S to M