@dokploy/mcp: All tool schemas inject `$schema: draft-07` causing Anthropic API 400 error

[elborky]

Bug Report

Summary

Every tool registered by @dokploy/mcp has an invalid input_schema that causes the Anthropic API to return a 400 error when the MCP is connected to Claude Code (or any Claude API client):

API Error: 400 {"type":"error","error":{"type":"invalid_request_error","message":"tools.22.custom.input_schema: JSON schema is invalid. It must match JSON Schema draft 2020-12 (https://json-schema.org/draft/2020-12). Learn more about tool use at https://docs.claude.com/en/docs/tool-use."},"request_id":"..."}

Root Cause

@dokploy/mcp uses zod-to-json-schema (via @modelcontextprotocol/sdk) which injects "$schema": "http://json-schema.org/draft-07/schema#" into every generated input_schema.

The Anthropic API requires tool input_schema to comply with JSON Schema draft 2020-12 and rejects any schema that declares itself as draft-07.

Affected file:

node_modules/@modelcontextprotocol/sdk/dist/esm/server/zod-json-schema-compat.js

The toJsonSchemaCompat function always injects $schema: draft-07 into the output.

Impact

• All 519 dokploy tools are affected — the first one encountered (tool index 22 in a typical Claude Code session) triggers the error
• The MCP cannot be used with Claude Code / Anthropic API at all until fixed

Versions

• @dokploy/mcp: latest (npx -y @dokploy/mcp)
• @modelcontextprotocol/sdk: v1.29.0
• zod-to-json-schema: v3.25.2

Proposed Fix

In the MCP server's tool registration layer, strip the $schema key from every generated input_schema before registering:

// After generating schema with zodToJsonSchema(...)
delete schema.$schema;

Or pass options to suppress $schema injection if/when zod-to-json-schema exposes that option in a future version.

Workaround (for users)

Remove dokploy from mcpServers in ~/.claude/settings.json until this is fixed.

[dosubot]

Hi @elborky! I'm Dosu and I’m helping the dokploy team.

This is a confirmed upstream issue in the @modelcontextprotocol/typescript-sdk. It's tracked as issue Dokploy/dokploy#745 in their repository — the SDK's zod-to-json-schema integration injects $schema: "draft-07" into every tool schema, which Anthropic's API rejects because it requires draft-2020-12.

The MCP TypeScript SDK is currently working toward a 2.0.0 release (alpha builds are available) which includes support for Standard Schema (Zod v4, Valibot, ArkType) that should address this [1].

In the meantime, for the @dokploy/mcp package specifically, the fix would be relatively straightforward. In server.ts, where tools are registered via server.tool(), the $schema key could be stripped after the SDK converts the Zod shape to JSON Schema — though since the conversion happens internally inside McpServer.tool(), the cleanest short-term fix would likely be to either:

1. Monkey-patch or wrap the SDK's internal zodToJsonSchema call to delete $schema from the output
2. Pin or upgrade @modelcontextprotocol/sdk to a version that includes a fix (once released)
3. Register tools with raw JSON Schema instead of Zod shapes, stripping $schema before passing them in

This issue likely belongs on the Dokploy/mcp repository since that's where the MCP server code lives [2], separate from the main Dokploy repo.

To reply, just mention @dosu.

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Docs are dead. Just use Dosu.

[AminDhouib]

Can confirm this is happening to us as well. It's a pretty critical bug which makes dokploy-mcp nearly unusable as chat breaks and you lose all of the progress you had on that chat.