---
title: "Keep task capabilities in their protocol version"
description: "Task capabilities from MCP 2025-11-25 and extension advertisements in MCP 2026-07-28 are not interchangeable fields. Limit each capability declaration to the versions that define i"
source: "https://mcpdesc.org/docs/rules/0.9.0-rc.3/mcp/capabilities-tasks-protocol-version/"
---

Task capabilities from MCP 2025-11-25 and extension advertisements in MCP 2026-07-28 are not interchangeable fields. Limit each capability declaration to the versions that define it. The validator does not automatically translate a tasks object into an extension advertisement.

## Requirement

The core tasks server capability exists only in MCP 2025-11-25; MCP 2026-07-28 uses the tasks extension instead.

## Details

**Rule ID:** `mcp.capabilities.tasks.protocol-version`  
**Owner:** mcp  
**Surface:** ServerCapabilities · **Path:** `tasks`  
**Kind:** structural  
**Requirement level:** must  
**Status:** internal · **Enforcement:** internal

## Protocol version applicability

| 2024-11-05 | 2025-03-26 | 2025-06-18 | 2025-11-25 | 2026-07-28 |
| ---------- | ---------- | ---------- | ---------- | ---------- |
| applies    | applies    | applies    | applies    | applies    |

## Required by

* **MCP Description 0.9.0, Section 8.3**  
  * 8\. Capabilities: [req-capabilities-tasks-distinct](https://mcpdesc.org/docs/specification/0.9.0-rc.3/capabilities#req-capabilities-tasks-distinct)
  * 1. Versioning: [req-field-protocol-version-availability](https://mcpdesc.org/docs/specification/0.9.0-rc.3/versioning#req-field-protocol-version-availability)

## Based on

* **Tier 1 — MCP schema.ts and normative specification text:** MCP 2025-11-25 schema.ts, ServerCapabilities tasks; MCP 2025-06-18 and 2026-07-28 schema.ts, ServerCapabilities (no tasks)  
  * [validation/mcp-schemas/2025-11-25/schema.ts#L430-L456](https://github.com/modelcontextprotocol/modelcontextprotocol/blob/dae694f61a31f7a3ec2af3aff709e11f70f61e48/schema/2025-11-25/schema.ts#L430-L456)
  * [validation/mcp-schemas/2025-06-18/schema.ts#L253-L302](https://github.com/modelcontextprotocol/modelcontextprotocol/blob/dae694f61a31f7a3ec2af3aff709e11f70f61e48/schema/2025-06-18/schema.ts#L253-L302)
  * [validation/mcp-schemas/2026-07-28/schema.ts#L788-L883](https://github.com/modelcontextprotocol/modelcontextprotocol/blob/dae694f61a31f7a3ec2af3aff709e11f70f61e48/schema/2026-07-28/schema.ts#L788-L883)

## Examples

### Invalid example

Source: [expected-invalid/tasks-capability-2026.json](https://github.com/mcpdesc/mcpdesc-specification/blob/v0.9.0-rc.3/spec/draft/fixtures/expected-invalid/tasks-capability-2026.json) · Selected: `/capabilities/0`

```json
{
  "tasks": {
    "list": {}
  }
}
```

## Rule Source Code

[capabilities.yaml](https://github.com/mcpdesc/mcpdesc-specification/blob/v0.9.0-rc.3/spec/draft/validation/rules/capabilities.yaml) at immutable tag [v0.9.0-rc.3](https://github.com/mcpdesc/mcpdesc-specification/blob/v0.9.0-rc.3/spec/draft).