refactor: fix CI, use zod v4, and latest method in mcp

[lumirlumir]

Prerequisites checklist

• I have read the contributing guidelines.

What is the purpose of this pull request?

In this PR, I've made several updates, particularly for @eslint/mcp.

Unfortunately, some of the problems have recently arisen in the rewrite repository, so this PR includes a bit of changes especially for @eslint/mcp.

This PR includes the following fixes:

1. Upgrade @modelcontextprotocol/sdk to v1.23.0 and zod to v4

Two days ago, @modelcontextprotocol/sdk@1.23.0 was released.

https://github.com/modelcontextprotocol/typescript-sdk/releases/tag/1.23.0

Shortly after that release, our CI began failing with the TS2589: Type instantiation is excessively deep and possibly infinite error.

I tried to resolve it myself but couldn't find a suitable solution, so I opened an issue in @modelcontextprotocol/sdk: modelcontextprotocol/typescript-sdk#1180

The issue was traced to the newly introduced Zod v4 support in @modelcontextprotocol/sdk@1.23.0.

This only affected the eslint/rewrite repository because the dev-dependency knip uses Zod v4 internally, while @eslint/mcp depends on Zod v3, causing a version conflict. The SDK team provided a clear explanation here: modelcontextprotocol/typescript-sdk#1180 (comment)

To avoid the conflict, I've bumped Zod to v4. Zod v4 offers v3 compatibility via zod/v3, so no code changes were necessary.

2. Replace deprecated mcpServer.tool usage with mcpServer.registerTool

Per the JSDoc comments in @modelcontextprotocol/sdk, mcpServer.tool is deprecated, so I've replaced it with the recommended mcpServer.registerTool.

3. The recently released prettier@3.7.1 has caused formatting errors:

Yesterday, prettier@3.7.1 was released and caused formatting errors, particularly in .ts files.

I've updated it accordingly, which introduced some additional code diffs.

What changes did you make? (Give an overview)

In this PR, I've fixed CI and use zod v4, and latest method in mcp

Related Issues

Ref: modelcontextprotocol/typescript-sdk#1180 (comment)

Is there anything you'd like reviewers to focus on?

The behavior of MCP has not changed, so I've marked the prefix as refactor, though I'm not sure about that.

[lumirlumir]

The CI failure appears to be a regression in @modelcontextprotocol/sdk@1.23.0, which was released yesterday.

I've opened an issue about it in @modelcontextprotocol/sdk: modelcontextprotocol/typescript-sdk#1180

[lumirlumir]

If I don't add these two lines, the tests fail, so I've added them.

However, I'm not sure whether this is considered a user-facing change.

[fasttime]

I think it's fine to re-add these lines. These were removed in commit 45842c0 to fix compatibility with version 1.22.0 of @modelcontextprotocol/sdk.

[fasttime]

With @modelcontextprotocol/sdk 1.23.0, the build completes without issues. Anyway, with version 1.24.1 (latest at the time of writing), I'm getting a type error:

$ npm run build

> @eslint/mcp@0.2.0 build
> tsc

../../node_modules/@modelcontextprotocol/sdk/dist/esm/server/index.d.ts:1:25 - error TS7016: Could not find a declaration file for module 'express'. '.../rewrite/node_modules/express/index.js' implicitly has an 'any' type.
  Try `npm i --save-dev @types/express` if it exists or add a new declaration (.d.ts) file containing `declare module 'express';`

1 import { Express } from 'express';
                          ~~~~~~~~~


Found 1 error in ../../node_modules/@modelcontextprotocol/sdk/dist/esm/server/index.d.ts:1

The error can be fixed by installing @types/express as the message suggests.

[lumirlumir]

I've updated it in 8ad6bc6 👍

Also, I've added @types/express to the ignoreDependencies for knip in fb2b0dd, because knip reported an error indicating that the dependency was unused.

[fasttime]

Overall, my impression is that @modelcontextprotocol/sdk isn't very mature, considering that each of the last three minor releases (1.22.0, 1.23.0 and 1.24.0) seems to introduce a new incompatibility. If this trend continues, I'd suggest shrinking the version range for that package with a tilde.

[Copilot]

Pull request overview

This PR addresses CI failures caused by TypeScript type instantiation errors and updates dependencies to resolve version conflicts. The primary issue stemmed from @modelcontextprotocol/sdk v1.23.0 introducing Zod v4 support, which conflicted with the repository's use of both Zod v3 (in @eslint/mcp) and Zod v4 (used internally by knip). The PR upgrades to Zod v4 with v3 compatibility, updates the MCP SDK to the latest version, and incorporates formatting changes from a newer Prettier release.

Key changes:

• Upgraded zod from v3.24.4 to v4.1.13 using the zod/v3 compatibility import path
• Updated @modelcontextprotocol/sdk to v1.24.1 and migrated from deprecated mcpServer.tool() to mcpServer.registerTool()
• Updated prettier to v3.7.3, resulting in formatting adjustments to TypeScript files

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
packages/mcp/package.json	Updated dependencies: @modelcontextprotocol/sdk to v1.24.1, zod to v4.1.13, prettier to v3.7.3; added @types/express devDependency
packages/mcp/src/mcp-server.js	Changed zod import to use v3 compatibility layer and migrated to registerTool() API
packages/mcp/tests/mcp-server.test.js	Updated JSON schema assertion to include $schema and additionalProperties fields required by new SDK version
packages/core/tests/types/types.test.ts	Prettier formatting adjustments to TypeScript generic type declarations
packages/core/src/types.ts	Prettier formatting adjustments to TypeScript interface declarations
package.json	Updated prettier to v3.7.3 in root package.json

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[fasttime]

LGTM, thanks! I've verified that the MCP server behaves as expected after these changes.