fix(filesystem): emit object input schemas

[Tiancheng-Xu]

Description

Closes #4772.

server-filesystem registered tools with raw Zod shapes (Schema.shape or inline field objects). With older SDK schema conversion, that representation can omit the root type: "object" from the JSON Schema returned by tools/list, causing strict JSON Schema 2020-12 clients to reject the server.

This change:

• registers every filesystem tool with a complete z.object(...) schema;
• adds a real stdio MCP regression test that calls tools/list and checks every tool's inputSchema.type.

No tool arguments or unrelated servers were changed.

How Has This Been Tested?

• npm run build — passed for all workspaces.
• cd src/filesystem && npx vitest run --coverage __tests__/tools-list-schema.test.ts — passed, 1 test.
• The focused non-Unicode filesystem suite — passed, 166 tests across 10 files.
• The complete filesystem suite — 166 passed and 3 pre-existing macOS Unicode-path failures. The failures are caused by /var vs /private/var realpath handling and NFD/NFC directory behavior; the same 3 failures reproduce on the parent commit.
• The published @modelcontextprotocol/server-filesystem@2025.8.21 baseline reproduces the reported strict-client failure for all 13 tools (inputSchema.type is missing).

The new regression test passes on the current repository baseline because the current @modelcontextprotocol/sdk@1.30.0 compatibility layer normalizes raw shapes. The implementation removes that dependency on implicit SDK behavior for future releases.

Breaking Changes

None. Tool names, arguments, and handlers are unchanged.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature
• Breaking change
• Documentation update

Checklist

• I have read the MCP Protocol Documentation
• My changes follow MCP security best practices
• I have updated the server's README accordingly (not applicable)
• I have tested this with an LLM client (the regression uses the MCP SDK stdio client)
• My code follows the repository's style guidelines
• Targeted and unaffected existing tests pass locally
• No new error-handling path was introduced
• Environment variables or configuration options are not applicable

AI assistance disclosure

This PR was prepared with OpenAI Codex under human direction. The final diff, test evidence, and issue/PR state were reviewed before submission.

中文说明

关闭 #4772。filesystem 原先把裸 Zod shape 注册给 SDK；在受影响的旧 SDK 转换路径中，tools/list 返回的 JSON Schema 会缺少根级 type: "object"，严格的 JSON Schema 2020-12 客户端因此拒绝启动。本 PR 将全部 filesystem 工具改为使用完整的 z.object(...) schema，并增加真实 stdio MCP tools/list 回归测试，确认每个工具都声明 inputSchema.type: "object"。工具名称、参数和处理器保持不变。完整测试中的 3 个 Unicode 路径失败在父提交上也能复现，属于当前 macOS 环境基线问题，未将其写成通过。

[Copilot]

🟢 Approval recommended

The change is a small, well-scoped schema fix whose 14 substitutions are each semantically equivalent to prior definitions, matches an existing repo convention, and is covered by a regression test following an established pattern.

Pull request overview

This PR fixes a JSON Schema compliance bug in server-filesystem (issue #4772), where tools/list responses could omit the required root type: "object" from each tool's inputSchema, causing strict JSON Schema 2020-12 clients (e.g. Claude Desktop's "Cowork and Code" shared pool) to reject the server. It converts every tool registration from raw Zod shapes (Schema.shape / inline field objects) to complete z.object(...) schemas, and adds a real stdio MCP regression test that asserts every tool advertises inputSchema.type: "object".

Changes:

• Replaces raw Zod shapes / inline field objects with the already-defined z.object(...) named schemas across all 14 filesystem tool registrations (and z.object({}) for list_allowed_directories).
• Adds __tests__/tools-list-schema.test.ts, which spawns the built server over stdio, calls tools/list, and checks each tool's inputSchema.type.

File summaries

File	Description
src/filesystem/index.ts	Registers every tool with a full z.object(...) input schema instead of a raw shape/.shape, ensuring the root type: "object" is emitted.
src/filesystem/tests/tools-list-schema.test.ts	New stdio MCP regression test verifying every tool's inputSchema.type is "object".

Notes from verification:

• All 14 substituted schemas are semantically equivalent to the inline definitions they replace (schemas defined at index.ts:97-161); handlers already typed their args via z.infer<typeof …Schema>, so this also removes duplication.
• Passing a z.object(...) (ZodObject) directly to registerTool's inputSchema matches the existing repo convention (src/everything/tools/echo.ts:15), so it is the idiomatic form.
• The new test mirrors the existing directory-tree.mcp-sdk.test.ts pattern (spawning ../dist/index.js), so its build dependency is not a new concern.

Review details

• Files reviewed: 2/2 changed files
• Comments generated: 0
• Review effort level: Balanced

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