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Model Context Protocol resources and the caching utility

Verified 2026-09-30 · 13 sources · tier 1 · 1 disputed

Also known as cacheable operations, resource template, resources/subscribe.

Disputed: 1 source below carries conflicting evidence.

The Model Context Protocol caching utility enumerates 6 cacheable operations, including server discovery, the tools list, the prompts list, the resources list, the resource templates list, and resource read 13. Under the protocol's subscription model, the subscriptions listen stream replaces the former resources subscribe request, unifying resource subscriptions and tool list notifications under one filter-based mechanism 8.

Protocol operations and subscription mechanism

The caching specification defines 6 operations eligible for caching: server discovery, the tools list, the prompts list, the resources list, the resource templates list, and resource read 13. In the field, the caching page's freshness formula survives only as its first token in this corpus's extracted text and must be read from the raw payload 7.

The subscriptions listen stream replaces the earlier resources subscribe request, allowing resource subscriptions and tool list notifications to share a single filter-based mechanism instead of operating in parallel 8. Additionally, the subscriptions specification mandates that a server MUST NOT send notification types that the client has not explicitly requested 9.

Notification handling and specification differences

This is disputed, as the Resources page's list changed notification section lacks the clause carried by both the Tools and Prompts pages restricting delivery to clients holding a subscriptions listen stream 11. Furthermore, the message flow diagram on the Resources page omits a list changed flow entirely, whereas the diagram on the Prompts page displays one within an optional fragment 10.

The Resources page does not define what happens to a notifiable event that occurs when no client holds a matching subscription, containing no queueing, retention, or replay language across its prose, code samples, or diagrams 12.

See also

See also The MCP subscriptions listen stream and notification delivery. See also Whether a cached tool list defeats a change notification. See also The Model Context Protocol server discovery operation. See also Fidelity of the corpus text extraction pipeline.

Applicability

Applies to: Model Context Protocol Project. Sources checked 2026-09-05. Specific release numbers and region exclusions are not covered by the sources below.

What remains uncertain

Whether a cached tools list defeats a list changed notification is not covered by the sources below. The Resources page does not state what becomes of a notifiable event that occurs while no client holds a matching subscription, and its prose, code samples, and diagram contain no queueing, retention, or replay language 12. What becomes of an event with no subscriber is not covered by the sources below. Whether any host documents its own answer to the delivery gap is not covered by the sources below. Why the Resources page omits the delivery qualifier its siblings carry is not covered by the sources below. What invalidates a cached entry besides expiry is not covered by the sources below. How a cursor behaves when a page changes mid traversal is not covered by the sources below. What a resource template is is not covered by the sources below. Whether prompts carry the same delivery weaknesses as tools is not covered by the sources below.

See also

Parent of

Related to

Scopes

Referenced by

Sources

  1. 1
    The Caching page diagram draws the list_changed notification with the '-->>' arrow, whereas the Tools page diagram of the same specification revision draws it with the '--)' arrow.
    Model Context Protocol specification 2026-07-28, Caching · Interaction with Notifications, mermaid block, line 'Server-->>Client: notifications/tools/list_changed' · Checked 2026-09-30
  2. 2
    The 2026-07-28 Caching page carries a mermaid sequenceDiagram under Interaction with Notifications that works through a timeline: a tools/list result with ttlMs 300000 is used from cache at two minutes, re-fetched after expiry, and invalidated immediately by a list_changed notification.
    Model Context Protocol specification 2026-07-28, Caching · Interaction with Notifications, mermaid block · Checked 2026-09-30
  3. 3
    The Caching page's Freshness Calculation subsection contains a fenced code block with no language tag whose content is the single expression 'now < t_received + ttlMs'.
    Model Context Protocol specification 2026-07-28, Caching · Cacheable Model > Time-to-Live (TTL) Field > Freshness Calculation · Checked 2026-09-30
  4. 4
    The 2026-07-28 Resources page Message Flow section is a mermaid sequenceDiagram with no prose, and it shows subscriptions/listen (resourceSubscriptions) followed by notifications/subscriptions/acknowledged and then notifications/resources/updated.
    Model Context Protocol specification 2026-07-28, Resources · Message Flow · Checked 2026-09-30
  5. 5
    The 2026-07-28 Resources page embeds a PNG image (resource-picker.png) under User Interaction Model whose only textual representation in the served Markdown is the alt text 'Example of resource context picker'.
    Model Context Protocol specification 2026-07-28, Resources · User Interaction Model, img element after the bullet list · Checked 2026-09-30
  6. 6
    The Model Context Protocol caching page states that a relevant notification received while a cached response is still fresh invalidates that cached response, which should then be considered immediately stale.
    Model Context Protocol specification 2026-07-28, Caching · Interaction with Notifications, closing paragraph · Checked 2026-09-05
  7. 7
    The caching page's freshness formula survives only as its first token in this corpus's extracted text and must be read from the raw payload.field report
    Model Context Protocol specification 2026-07-28, Caching · Caching, freshness · Checked 2026-09-05
  8. 8
    The subscriptions listen stream replaces the former resources subscribe request, so resource subscriptions and tool list notifications now share one filter-based mechanism rather than running in parallel.
    Model Context Protocol specification 2026-07-28, Subscriptions · Subscriptions · Checked 2026-09-05
  9. 9
    The subscriptions page states that a server MUST NOT send notification types the client has not explicitly requested.
    Model Context Protocol specification 2026-07-28, Subscriptions · Subscriptions · Checked 2026-09-05
  10. 10
    The Resources page's message flow diagram omits a list changed flow entirely while the Prompts page's diagram shows one inside an optional fragment.
    Model Context Protocol specification 2026-07-28, Resources · Resources message flow diagram compared with the Prompts diagram · Checked 2026-09-05
  11. 11
    The Resources page's list changed notification section lacks the clause that the Tools and Prompts pages both carry restricting delivery to clients holding a subscriptions listen stream.disputed
    Model Context Protocol specification 2026-07-28, Resources · Resources, List Changed Notification compared with the Tools and Prompts pages · Checked 2026-09-05
  12. 12
    The Resources page does not state what becomes of a notifiable event that occurs while no client holds a matching subscription; no queueing, retention or replay language appears in its prose, its code samples or its diagram.
    Model Context Protocol specification 2026-07-28, Resources · whole page · Checked 2026-09-05
  13. 13
    The caching page enumerates 6 cacheable operations: server discovery, the tools list, the prompts list, the resources list, the resource templates list, and resource read.
    Model Context Protocol specification 2026-07-28, Caching · Caching, cacheable operations · Checked 2026-09-05

Documents

tier 1 standards and regulators

Model Context Protocol specification 2026-07-28, Caching

Model Context Protocol project · 2026-07-28 · accessed 2026-09-05

tier 1 standards and regulators

Model Context Protocol specification 2026-07-28, Resources

Model Context Protocol project · 2026-07-28 · accessed 2026-09-05

tier 1 standards and regulators

Model Context Protocol specification 2026-07-28, Subscriptions

Model Context Protocol project · 2026-07-28 · accessed 2026-09-05

Cite this page

APA

WarmTransfer. (2026, September 30). Model Context Protocol resources and the caching utility. WarmTransfer. https://warmtransfer.net/knowledge/mcp-resources-and-caching

BibTeX

@misc{warmtransfer-mcp-resources-and-caching,
  title  = {Model Context Protocol resources and the caching utility},
  author = {{WarmTransfer}},
  year   = {2026},
  url    = {https://warmtransfer.net/knowledge/mcp-resources-and-caching},
  note   = {Verified 2026-09-30}
}