protocol

mcp_prompt_protocol

Protocol for Logtalk objects that provide prompts to be exposed via an MCP (Model Context Protocol) server. Implementing objects must define the set of prompts available and handle prompt get requests. Prompts are templates for structured LLM interactions that can accept arguments to customize their behavior. Used by both the 2025-06-18 and 2026-07-28 adapters.

Availability:
logtalk_load(mcp_server(loader))
Author: Paulo Moura
Version: 1:0:0
Date: 2026-08-14
Compilation flags:
static
Dependencies:
(none)
Remarks:

  • Capabilities: Objects providing prompts must declare prompts in their capabilities/1 predicate (from the mcp_tool_protocol protocol). The server will then advertise the prompts capability and handle prompts/list and prompts/get requests.

  • Prompt descriptors: Each prompt is described by a prompt(Name, Description, Arguments) or prompt(Name, Title, Description, Arguments) term where Name is an atom, Title is an optional human-friendly display name (an atom), Description is a human-readable atom, and Arguments is a list of argument(ArgName, ArgDescription, Required) terms.

  • Prompt messages: The prompt_get/3 predicate must return a result term containing a list of messages. Each message is a message(Role, Content) term where Role is user or assistant and Content is text(Text) where Text is an atom.

  • Multi-round (2026-07-28): For the 2026-07-28 adapter, applications that need additional input during a prompt get implement prompt_get_round/4 from the mcp_multiround_protocol. Existing prompt_get/3 remains valid and is wrapped as a complete result when the round hook is absent.

Inherited public predicates:
(none)

Public predicates

prompts/1

Returns a list of prompt descriptors available from this object. Each descriptor is a compound term prompt(Name, Description, Arguments) or prompt(Name, Title, Description, Arguments) where Name is the MCP prompt name (an atom), Title is an optional human-friendly display name (an atom), Description is a human-readable description (an atom), and Arguments is a list of argument(ArgName, ArgDescription, Required) terms describing the prompt arguments. ArgName and ArgDescription are atoms, and Required is the boolean true or false.

Compilation flags:
static
Template:
prompts(Prompts)
Mode and number of proofs:
prompts(-list(compound)) - one

prompt_get/3

Handles a prompt get request. Name is the MCP prompt name (as declared in prompts/1), Arguments is a list of ArgumentName-Value pairs provided by the client, and Result is unified with the prompt result. The result must be one of: messages(MessageList) for a list of prompt messages, or messages(Description, MessageList) to also include a description. Each message in the list must be a message(Role, Content) term where Role is user or assistant and Content is text(Text) where Text is an atom.

Compilation flags:
static
Template:
prompt_get(Name,Arguments,Result)
Mode and number of proofs:
prompt_get(+atom,+list(pair),--compound) - one

Protected predicates

(none)

Private predicates

(none)

Operators

(none)