.. index:: single: mcp_cache_protocol
.. _mcp_cache_protocol/0:

.. rst-class:: right

**protocol**

``mcp_cache_protocol``
======================

Optional protocol for per-operation cache policy used by the MCP 2026-07-28 specification. An application may implement ``cache_policy/4`` to choose TTL (milliseconds) and scope (``public`` or ``private``) for complete results of ``server/discover``, list operations (``tools/list``, ``prompts/list``, ``resources/list``, ``resources/templates/list``), and ``resources/read``. Cache fields are never attached to ``input_required`` results or MRTR retries. When the predicate is not defined, or for an operation it does not cover, the server falls back to the options ``cache_ttl(0)`` and ``cache_scope(private)``.

| **Availability:** 
|    ``logtalk_load(mcp_server(loader))``

| **Author:** Paulo Moura
| **Version:** 1:0:0
| **Date:** 2026-08-14

| **Compilation flags:**
|    ``static``


| **Dependencies:**
|   (none)


| **Remarks:**

   - TTL: A non-negative integer number of milliseconds. ``0`` means the result must not be cached.
   - Scope: Either ``public`` (may be shared across clients) or ``private`` (client-specific).
   - Applicability: Only complete final results of discover, list, and resource-read operations receive cache fields. Tool calls, prompt gets that return ``input_required``, and any MRTR continuation never include ``ttlMs`` / ``cacheScope``.

| **Inherited public predicates:**
|    (none)

.. contents::
   :local:
   :backlinks: top

Public predicates
-----------------

.. index:: cache_policy/4
.. _mcp_cache_protocol/0::cache_policy/4:

``cache_policy/4``
^^^^^^^^^^^^^^^^^^

Returns the cache policy for a given operation and request. ``Operation`` is one of ``discover``, ``tools_list``, ``prompts_list``, ``resources_list``, ``resources_templates_list``, or ``resources_read``. ``Request`` is the request-specific identifier or arguments (e.g. a resource URI for ``resources_read``, or a free term for list/discover). ``TTL`` is a non-negative integer (milliseconds). ``Scope`` is ``public`` or ``private``. Failure means the server should use its configured defaults.

| **Compilation flags:**
|    ``static``

| **Template:**
|    ``cache_policy(Operation,Request,TTL,Scope)``
| **Mode and number of proofs:**
|    ``cache_policy(+atom,+term,-integer,-atom)`` - ``zero_or_one``


------------

Protected predicates
--------------------

(none)

Private predicates
------------------

(none)

Operators
---------

(none)