ConduitMcp.Capabilities (ConduitMCP v0.11.0)

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Builds the capabilities object a server advertises to MCP clients.

The base set comes from the server module's __capabilities__/0 when it defines one (typically generated by ConduitMcp.Endpoint); otherwise it is the plain tools/resources/prompts set with listChanged: false.

Flags for optional features are then overlaid according to which callbacks the server module exports:

  • resources.subscribe: true (legacy) — handle_subscribe_resource/2, and only when the base set advertises resources at all.
  • completions: %{} — handle_complete/3.
  • logging: %{} — handle_set_log_level/2 (legacy); always on the modern era, where any tool can emit notifications/message through ConduitMcp.Log on a request that sets a logLevel, and the 2026-07-28 spec requires a server that emits them to declare logging.
  • extensions: %{"io.modelcontextprotocol/tasks" => %{}} — modern era only, while ConduitMcp.Ext.Tasks is enabled.

Used for both the legacy initialize reply and the modern server/discover result (ConduitMcp.Discover). The two eras differ in change notifications:

  • legacy advertises the base set as is: this library has no legacy delivery path for list-changed notifications, and resources.subscribe means the server implements resources/subscribe.
  • modern sets listChanged: true on each of tools, prompts and resources it advertises, and subscribe: true on resources: every modern server answers subscriptions/listen (ConduitMcp.Subscriptions, always running), whose toolsListChanged/promptsListChanged/resourcesListChanged/ resourceSubscriptions filters deliver whatever the server pushes with ConduitMcp.notify_tools_changed/0 and friends.

The tasks extension is advertised on the modern era only.

Summary

Functions

build(server_module, opts \\ [])

Returns the capabilities map advertised for server_module.

Functions

build(server_module, opts \\ [])

@spec build(module(), keyword()) :: map()

Returns the capabilities map advertised for server_module.

Options:

  • :era — :legacy (default) or :modern; see the moduledoc. Modern may add the tasks extension.

Examples

ConduitMcp.Capabilities.build(MyServer)
#=> %{
#     "tools" => %{"listChanged" => false},
#     "resources" => %{"listChanged" => false},
#     "prompts" => %{"listChanged" => false}
#   }

ConduitMcp.Capabilities.build(MyServer, era: :modern)
#=> %{
#     "tools" => %{"listChanged" => true},
#     "resources" => %{"listChanged" => true, "subscribe" => true},
#     "prompts" => %{"listChanged" => true}
#   }