Add Smithery Playground to clients.mdx (modelcontextprotocol#1625)

* Add Smithery to clients.mdx

* Add missing link

* Apply suggestion from @jonathanhefner

Co-authored-by: Jonathan Hefner <[email protected]>

---------

Co-authored-by: Jonathan Hefner <[email protected]>
Co-authored-by: shaun smith <[email protected]>

Author: 3 people

docs/clients.mdx

@@ -83,6 +83,7 @@ This page provides an overview of applications that support the Model Context Pr
 | [Shortwave][Shortwave]                           | ❌          | ❌        | ✅      | ❓                     | ❌         | ❌    | ❓            |
 | [Simtheory][Simtheory]                           | ✅          | ✅        | ✅      | ✅                     | ❌         | ❌    | ❓            |
 | [Slack MCP Client][Slack MCP Client]             | ❌          | ❌        | ✅      | ❓                     | ❌         | ❌    | ❓            |
+| [Smithery Playground][Smithery Playground]       | ✅          | ✅        | ✅      | ❓                     | ❌         | ❌    | ❓            |
 | [SpinAI][SpinAI]                                 | ❌          | ❌        | ✅      | ❓                     | ❌         | ❌    | ❓            |
 | [Superinterface][Superinterface]                 | ❌          | ❌        | ✅      | ❓                     | ❌         | ❌    | ❓            |
 | [Superjoin][Superjoin]                           | ❌          | ❌        | ✅      | ❓                     | ❌         | ❌    | ❓            |
@@ -179,6 +180,7 @@ This page provides an overview of applications that support the Model Context Pr
 [Shortwave]: https://www.shortwave.com
 [Simtheory]: https://simtheory.ai
 [Slack MCP Client]: https://github.com/tuannvm/slack-mcp-client
+[Smithery Playground]: https://smithery.ai/playground
 [SpinAI]: https://spinai.dev
 [Superinterface]: https://superinterface.ai
 [Superjoin]: https://superjoin.ai
@@ -1052,6 +1054,18 @@ Simtheory is an agentic AI workspace that unifies multiple AI models, tools, and
 - **Dynamic and Secure Integration:** Supports dynamic registration of MCP tools, works in both channels and direct messages and manages credentials securely via environment variables or Kubernetes secrets.
 - **Easy Deployment and Extensibility:** Offers official Docker images, a Helm chart for Kubernetes, and Docker Compose for local development, making it simple to deploy, configure, and extend with additional MCP servers or tools.
 
+### Smithery Playground
+
+Smithery Playground is a developer-first MCP client for exploring, testing and debugging MCP servers against LLMs. It provides detailed traces of MCP RPCs to help troubleshoot implementation issues.
+
+**Key features:**
+
+- One-click connect to MCP servers via URL or from Smithery's registry
+- Develop MCP servers that are running on localhost
+- Inspect tools, prompts, resources, and sampling configurations with live previews
+- Run conversational or raw tool calls to verify MCP behavior before shipping
+- Full OAuth MCP-spec support
+
 ### SpinAI
 
 [SpinAI](https://spinai.dev) is an open-source TypeScript framework for building observable AI agents. The framework provides native MCP compatibility, allowing agents to seamlessly integrate with MCP servers and tools.