use mermaid diagrams

Author: kentcdodds

exercises/01.ping/01.problem.connect/README.mdx

@@ -19,4 +19,4 @@ comments.
 Right now if you try to run the server, you'll get an error. Let's fix that!
 
 - 📜 [MCP TypeScript SDK Docs](https://github.com/modelcontextprotocol/typescript-sdk)
-- 📜 [MCP Spec: Ping](https://modelcontextprotocol.io/specification/2025-03-26/basic/utilities/ping)
+- 📜 [MCP Spec: Ping](https://modelcontextprotocol.io/specification/2025-06-18/basic/utilities/ping)

exercises/01.ping/README.mdx

@@ -32,4 +32,4 @@ server.tool(
 </callout-success>
 
 - 📜
-  [MCP Spec: Tools](https://modelcontextprotocol.io/specification/2025-03-26/server/tools)
+  [MCP Spec: Tools](https://modelcontextprotocol.io/specification/2025-06-18/server/tools)

exercises/02.tools/02.problem.args/README.mdx

@@ -31,4 +31,4 @@ it is, throw an error with a descriptive message and then try it out in the
 inspector. You'll notice the `isError` field is set to `true` and the content is
 the helpful error message you provided.
 
-- [📜 MCP Spec: Errors](https://modelcontextprotocol.io/specification/2025-03-26/server/tools#error-handling)
+- [📜 MCP Spec: Errors](https://modelcontextprotocol.io/specification/2025-06-18/server/tools#error-handling)

exercises/02.tools/03.problem.errors/README.mdx

@@ -24,4 +24,4 @@ provide richer, more actionable results.
 To test this out, create a new tag and notice the resource is included in the
 response.
 
-- 📜 [MCP Spec: Tools (Embedded Resources)](https://modelcontextprotocol.io/specification/2025-03-26/server/tools#embedded-resources)
+- 📜 [MCP Spec: Tools (Embedded Resources)](https://modelcontextprotocol.io/specification/2025-06-18/server/tools#embedded-resources)