---
title: "Use MCP content blocks and resource contents"
description: "Content in example results is an MCP content block selected by type: text, image, audio, resource link, or embedded resource. Resource contents have a uri and either text or blob. "
source: "https://mcpdesc.org/docs/rules/0.9.0-rc.3/mcp/content-members/"
---

Content in example results is an MCP content block selected by type: text, image, audio, resource link, or embedded resource. Resource contents have a uri and either text or blob. Each carries only the fields its MCP type defines.

## Requirement

Content blocks and resource contents match exactly one MCP content type, with its required fields and no unknown fields.

## Details

**Rule ID:** `mcp.content.members`  
**Owner:** mcp  
**Surface:** ContentBlock, ResourceContents  
**Kind:** structural  
**Requirement level:** must  
**Protocol versions:** independent of the MCP protocol version  
**Document schema locations:** `#/$defs/toolResultContent`, `#/$defs/resourceContents`  
**Status:** internal · **Enforcement:** internal

## Required by

* **MCP Description 0.9.0, Section 3.6**  
  * 3\. Document Structure: [req-carried-defined-fields](https://mcpdesc.org/docs/specification/0.9.0-rc.3/document-structure#req-carried-defined-fields)
  * 1. Document Structure: [req-carried-closed-reject](https://mcpdesc.org/docs/specification/0.9.0-rc.3/document-structure#req-carried-closed-reject)
  * 1. Resources and Resource Templates: [req-resource-annotations-not-in-examples](https://mcpdesc.org/docs/specification/0.9.0-rc.3/resources#req-resource-annotations-not-in-examples)
  * 1. Resources and Resource Templates: [req-resource-contents-fields](https://mcpdesc.org/docs/specification/0.9.0-rc.3/resources#req-resource-contents-fields)

## Based on

* **Tier 1 — MCP schema.ts and normative specification text:** MCP 2025-11-25 and 2026-07-28 schema.ts, ContentBlock and ResourceContents  
  * [validation/mcp-schemas/2025-11-25/schema.ts#L1740-L1741](https://github.com/modelcontextprotocol/modelcontextprotocol/blob/dae694f61a31f7a3ec2af3aff709e11f70f61e48/schema/2025-11-25/schema.ts#L1740-L1741)
  * [validation/mcp-schemas/2025-11-25/schema.ts#L881-L897](https://github.com/modelcontextprotocol/modelcontextprotocol/blob/dae694f61a31f7a3ec2af3aff709e11f70f61e48/schema/2025-11-25/schema.ts#L881-L897)
  * [validation/mcp-schemas/2026-07-28/schema.ts#L2305-L2306](https://github.com/modelcontextprotocol/modelcontextprotocol/blob/dae694f61a31f7a3ec2af3aff709e11f70f61e48/schema/2026-07-28/schema.ts#L2305-L2306)
  * [validation/mcp-schemas/2026-07-28/schema.ts#L1514-L1527](https://github.com/modelcontextprotocol/modelcontextprotocol/blob/dae694f61a31f7a3ec2af3aff709e11f70f61e48/schema/2026-07-28/schema.ts#L1514-L1527)

## Examples

### Invalid example

Source: [expected-invalid/discriminated-union-members.json](https://github.com/mcpdesc/mcpdesc-specification/blob/v0.9.0-rc.3/spec/draft/fixtures/expected-invalid/discriminated-union-members.json) · Selected: `/tools/0/interactionExamples/invalid/result/content/0`

```json
{
  "type": "text",
  "tetx": "Done"
}
```

## 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).