Extensions Overview changedextensions/overview
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99Extensions are identified using a unique *extension identifier* with the format: `{vendor-prefix}/{extension-name}`, e.g. `io.modelcontextprotocol/oauth-client-credentials`. Identifiers follow the same rules as [`_meta` keys](/specification/draft/basic/index#meta), with a mandatory prefix. Official extensions use the `io.modelcontextprotocol` vendor prefix.
1010
11<Tip>
12 If you're building a third-party extension, use a reversed domain name you own as the vendor prefix to avoid collisions (similar to Java package naming). For example, a company owning `example.com` would use `com.example/` as their prefix (e.g., `com.example/my-extension`).
13</Tip>
11> [!TIP]
12>
13> If you're building a third-party extension, use a reversed domain name you own as the vendor prefix to avoid collisions (similar to Java package naming). For example, a company owning `example.com` would use `com.example/` as their prefix (e.g., `com.example/my-extension`).
1414
1515## Official Extension Repositories
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1818
1919### MCP Authorization Extensions
2020
21<Card title="modelcontextprotocol/ext-auth" icon="github" href="https://github.com/modelcontextprotocol/ext-auth">
22 Extensions for supplementary authorization mechanisms beyond the core
23 specification.
24</Card>
21> **[modelcontextprotocol/ext-auth](https://github.com/modelcontextprotocol/ext-auth)**
22>
23> Extensions for supplementary authorization mechanisms beyond the core
24> specification.
2525
2626| Extension | Description |
2727| - | - |
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3030
3131### MCP Apps
3232
33<Card title="modelcontextprotocol/ext-apps" icon="github" href="https://github.com/modelcontextprotocol/ext-apps">
34 Extensions for interactive UI elements in conversational MCP clients.
35</Card>
33> **[modelcontextprotocol/ext-apps](https://github.com/modelcontextprotocol/ext-apps)**
34>
35> Extensions for interactive UI elements in conversational MCP clients.
3636
3737| Extension | Description |
3838| - | - |
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4848
4949### Skills over MCP
5050
51<Card title="modelcontextprotocol/ext-skills" icon="github" href="https://github.com/modelcontextprotocol/ext-skills">
52 Discover and read Agent Skills from MCP servers.
53</Card>
51> **[modelcontextprotocol/ext-skills](https://github.com/modelcontextprotocol/ext-skills)**
52>
53> Discover and read Agent Skills from MCP servers.
5454
5555| Extension | Description |
5656| - | - |
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9494
9595SDKs can choose to implement extensions, but it's not required for protocol conformance. SDK maintainers have full autonomy over which extensions they support. Where an SDK does support extensions, SDK documentation should list which extensions are supported.
9696
97<Note>
98 Extensions are always disabled by default and require explicit opt-in from the developer.
99</Note>
97> [!NOTE]
98>
99> Extensions are always disabled by default and require explicit opt-in from the developer.
100100
101101### Evolution
102102
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