class ActionController::MCPServer::Protocol

• ActionController::MCPServer::Protocol
• Reference
• Object

Overview

implements the MCP methods. Requests are independent, there are no sessions, so the results only depend on the request and the path params bound from its URL

Defined in:

action-controller/mcp/protocol.cr

Constant Summary

CACHEABLE = {"server/discover", "tools/list", "prompts/list", "resources/list", "resources/templates/list", "resources/read"}

methods whose results clients can cache, 2026-07-28 onwards

META_TOOLS = {"{\"name\":\"list_toolboxes\",\"description\":\"Lists the available toolboxes, each groups related tools and prompts\",\"inputSchema\":{\"type\":\"object\",\"properties\":{}},\"annotations\":{\"readOnlyHint\":true}}", "{\"name\":\"open_toolbox\",\"description\":\"Returns the definitions of the tools in a toolbox and the names of its prompts\",\"inputSchema\":#{TOOLBOX_ARGS},\"annotations\":{\"readOnlyHint\":true,\"idempotentHint\":true}}"}

PROXY_ARGS = "{\"type\":\"object\",\"properties\":{\"name\":{\"type\":\"string\",\"description\":\"the tool name, as returned by open_toolbox\"},\"arguments\":{\"type\":\"object\",\"description\":\"the tool arguments, matching its inputSchema\"}},\"required\":[\"name\"]}"

PROXY_TOOLS = {"{\"name\":\"call_read_only\",\"description\":\"Runs a tool that only reads data (proxy: call_read_only) from a toolbox, as returned by open_toolbox\",\"inputSchema\":#{PROXY_ARGS},\"annotations\":{\"readOnlyHint\":true,\"openWorldHint\":false}}", "{\"name\":\"call_tool\",\"description\":\"Runs a tool that can change data (proxy: call_tool) from a toolbox, as returned by open_toolbox. Prefer call_read_only for tools that only read data\",\"inputSchema\":#{PROXY_ARGS},\"annotations\":{\"readOnlyHint\":false,\"openWorldHint\":false}}"}

TOOLBOX_ARGS = "{\"type\":\"object\",\"properties\":{\"name\":{\"type\":\"string\",\"description\":\"the toolbox name, as returned by list_toolboxes\"}},\"required\":[\"name\"]}"

Constructors

• .new(invoker : Invoker, endpoint : String | Nil = nil, composition : Composition = Composition.default)

  endpoint is the path template of a controller endpoint, nil for the global server

Instance Method Summary

• #cache_ttl(method : String, params : Hash(String, JSON::Any)) : Time::Span

  how long the result can be cached, resource templates can set their own

• #discover_result(request : HTTP::Request | Nil = nil, bound : Hash(String, String) = {} of String => String) : String

  the server/discover result, the server info is in the result's _meta

• #flat? : Bool

  a controller endpoint lists every tool directly, there are no toolboxes

• #handle(method : String, params : Hash(String, JSON::Any), request : HTTP::Request, bound : Hash(String, String), modern : Bool = false) : String

  returns the JSON result of the request.

• #handle_streamed(method : String, params : Hash(String, JSON::Any), request : HTTP::Request, bound : Hash(String, String), modern : Bool = false) : String | StreamedResult

  returns the JSON result of the request, or a StreamedResult for long running routes, which the caller must close

• #initialize_result(protocol_version : String, request : HTTP::Request | Nil = nil, bound : Hash(String, String) = {} of String => String) : String

  the initialize result for the negotiated protocol version, before 2026-07-28

• #long_running?(method : String, params : Hash(String, JSON::Any)) : Bool

  true if the request runs a long running route, which is streamed

• #server_info(json : JSON::Builder, request : HTTP::Request | Nil = nil) : Nil

  the server's Implementation, its name, version and icons

• #subscribable?(uri : String) : Tuple(Tool, Hash(String, String)) | Nil

  the subscribable resource tool matching the URI, and its template variables

Constructor Detail

Instance Method Detail