---
title: "Use content blocks supported by each protocol version"
description: "Tool and Prompt examples carry native MCP content, whose types and fields vary by protocol version. Check each block against the containing declaration's full effective scope. A bl"
source: "https://mcpdesc.org/docs/rules/0.9.0-rc.3/mcp/content-block-protocol-version/"
---

Tool and Prompt examples carry native MCP content, whose types and fields vary by protocol version. Check each block against the containing declaration’s full effective scope. A block valid in a newer version is not automatically valid in an older one.

## Requirement

Content blocks in example results use only content types and fields the applicable protocol version defines: audio from MCP 2025-03-26, resource links and block \_meta from 2025-06-18, and resource-link icons from 2025-11-25.

## Details

**Rule ID:** `mcp.content-block.protocol-version`  
**Owner:** mcp  
**Surface:** ContentBlock  
**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, Sections 9.3 and 11.3**  
  * 9\. Tools: [req-tool-example-content-protocol-version](https://mcpdesc.org/docs/specification/0.9.0-rc.3/tools#req-tool-example-content-protocol-version)
  * 1. Prompts: [req-prompt-example-content-protocol-version](https://mcpdesc.org/docs/specification/0.9.0-rc.3/prompts#req-prompt-example-content-protocol-version)

## Based on

* **Tier 1 — MCP schema.ts and normative specification text:** MCP 2024-11-05 schema.ts, TextContent, ImageContent, and EmbeddedResource (no AudioContent, no ResourceLink, no content \_meta)  
  * [validation/mcp-schemas/2024-11-05/schema.ts#L842-L851](https://github.com/modelcontextprotocol/modelcontextprotocol/blob/dae694f61a31f7a3ec2af3aff709e11f70f61e48/schema/2024-11-05/schema.ts#L842-L851)
  * [validation/mcp-schemas/2024-11-05/schema.ts#L853-L868](https://github.com/modelcontextprotocol/modelcontextprotocol/blob/dae694f61a31f7a3ec2af3aff709e11f70f61e48/schema/2024-11-05/schema.ts#L853-L868)
  * [validation/mcp-schemas/2024-11-05/schema.ts#L610-L619](https://github.com/modelcontextprotocol/modelcontextprotocol/blob/dae694f61a31f7a3ec2af3aff709e11f70f61e48/schema/2024-11-05/schema.ts#L610-L619)
* **Tier 1 — MCP schema.ts and normative specification text:** MCP 2025-03-26 schema.ts, AudioContent  
  * [validation/mcp-schemas/2025-03-26/schema.ts#L987-L1009](https://github.com/modelcontextprotocol/modelcontextprotocol/blob/dae694f61a31f7a3ec2af3aff709e11f70f61e48/schema/2025-03-26/schema.ts#L987-L1009)
* **Tier 1 — MCP schema.ts and normative specification text:** MCP 2025-06-18 schema.ts, ResourceLink and ContentBlock, \_meta on content types  
  * [validation/mcp-schemas/2025-06-18/schema.ts#L753-L762](https://github.com/modelcontextprotocol/modelcontextprotocol/blob/dae694f61a31f7a3ec2af3aff709e11f70f61e48/schema/2025-06-18/schema.ts#L753-L762)
  * [validation/mcp-schemas/2025-06-18/schema.ts#L1130-L1134](https://github.com/modelcontextprotocol/modelcontextprotocol/blob/dae694f61a31f7a3ec2af3aff709e11f70f61e48/schema/2025-06-18/schema.ts#L1130-L1134)
* **Tier 1 — MCP schema.ts and normative specification text:** MCP 2025-11-25 schema.ts, Resource extends Icons (inherited by ResourceLink)  
  * [validation/mcp-schemas/2025-11-25/schema.ts#L797-L838](https://github.com/modelcontextprotocol/modelcontextprotocol/blob/dae694f61a31f7a3ec2af3aff709e11f70f61e48/schema/2025-11-25/schema.ts#L797-L838)

## Notes

The same diagnostic codes also report embedded resource \_meta (mcp.resource-contents.meta.protocol-version) and annotations.lastModified (mcp.annotations.last-modified.protocol-version); the rule property identifies which.

## Examples

### Invalid example

Source: [expected-invalid/protocol-version-incompatible-tool-example.json](https://github.com/mcpdesc/mcpdesc-specification/blob/v0.9.0-rc.3/spec/draft/fixtures/expected-invalid/protocol-version-incompatible-tool-example.json) · Selected: `/tools/0/examples/future-result/result/content/0`

```json
{
  "type": "resource_link",
  "uri": "resource://example/item",
  "name": "Future resource link"
}
```

### Invalid example

Source: [expected-invalid/invalid-prompt-example-semantics.json](https://github.com/mcpdesc/mcpdesc-specification/blob/v0.9.0-rc.3/spec/draft/fixtures/expected-invalid/invalid-prompt-example-semantics.json) · Selected: `/prompts/4/examples/resource-link-too-new/result/messages/0/content`

```json
{
  "type": "resource_link",
  "uri": "briefing://example",
  "name": "Example"
}
```

## Rule Source Code

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