McpServer.registerTool() does not support icons field from ToolScheme

[sainathreddyb]

Describe the bug

The MCP spec's ToolSchema includes IconsSchema.shape, making icons a valid top-level property on tool definitions. However, the high-level McpServer.registerTool() API has two gaps:

1. The config parameter type only accepts title, description, inputSchema, outputSchema, annotations, and _meta — icons is not included.
2. The setToolRequestHandlers listing handler in mcp.js does not include icons when building the toolDefinition object for tools/list responses.

To Reproduce

1. Create an MCP server using @modelcontextprotocol/sdk@1.29.0
2. Attempt to pass icons in the registerTool config:

server.registerTool(
  "my-tool",
  {
    title: "My Tool",
    description: "A tool with an icon",
    icons: [
      {
        src: "https://example.com/icon.png",
        mimeType: "image/png",
      },
    ],
  },
  async () => {
    return { content: [{ type: "text", text: "hello" }] };
  }
);

3. TypeScript reports a type error — icons is not a valid property on the config object.
4. Even if icons is forced onto the registered tool object, the tools/list response handler does not serialize it:

// In setToolRequestHandlers (mcp.js)
const toolDefinition = {
    name,
    title: tool.title,
    description: tool.description,
    inputSchema: /* ... */,
    annotations: tool.annotations,
    execution: tool.execution,
    _meta: tool._meta
    // icons is missing here
};

Expected behavior

registerTool should accept an optional icons array in its config, and the tool listing handler should include icons in the tools/list response — matching the spec's ToolSchema:

export const ToolSchema = z.object({
  ...BaseMetadataSchema.shape,
  ...IconsSchema.shape,  // <-- icons is part of the spec
  description: z.string().optional(),
  // ...
});

Logs

N/A — this is a type-level and serialization gap, not a runtime error.

Additional context

• SDK version: @modelcontextprotocol/sdk@1.29.0
• The server-level Implementation object correctly supports icons, websiteUrl, and description. The gap is only in the tool-level registerTool API and its listing handler.
• Current workaround: passing icons via _meta gets them into the response, but not at the spec-expected top-level location in the tool definition.

[sainathreddyb]

The ToolSchema includes icons via IconsSchema, but the high-level
registerTool() and registerToolTask() APIs did not accept or pass
through the icons field. This meant tools/list responses never
included icons even when the spec supports them.

Implementation is straight forward and includes doing following steps:

• Add icons to RegisteredTool type and update() method
• Add icons parameter to _createRegisteredTool()
• Add icons to registerTool() and registerToolTask() config types
• Include icons in toolDefinition for tools/list responses

Should I raise a PR with my implementation?