protocol

mcp_prompt_protocol

Protocol for Logtalk objects that provide prompts to be exposed via an MCP (Model Context Protocol) server. Implements the MCP 2025-06-18 specification. 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.

Availability:
logtalk_load(mcp_server(loader))
Author: Paulo Moura
Version: 0:2:0
Date: 2026-02-24
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.

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)