Use latest MCP sdk to fix zod-to-json-schema workaround

[christian-kreuzberger-dtx]

With #248 and #250 we have added a workaround for some issues with zod and zod-to-json-schema.

In the meantime, MCP sdk has working on a fix aswell: modelcontextprotocol/typescript-sdk#1040

Once this fix has been released, we should incorporate it, and hopefully revert the workaround.

[armchairdeity]

I found 2 separate issues with Zod... one is the version issue, 3.25 vs 4.x.

The other one is schema validation issues relating to metadata properties... which one is this fixing?

After fixing the Zod 4.x → 3.x downgrade issue, a new validation error occurred:

ERROR: Your input to the tool was invalid (must NOT have additional properties)

All Dynatrace MCP tools with parameters were failing, while parameter-free tools worked correctly.

Root Cause

Two-layer validation issue:

1. Schema Generation: The MCP SDK generates JSON schemas from Zod schemas using zodToJsonSchema(tool.inputSchema, { strictUnions: true, pipeStrategy: 'input' }). This creates schemas where
   nested objects implicitly have additionalProperties: false.

2. Client-side Validation: The VS Code MCP client (GitHub Copilot) adds metadata properties when invoking tools. These properties are validated against the generated schemas before the request
   is sent to the server.

3. Server-side Validation: Even if the request reaches the server, Zod validates input using .safeParseAsync(), which by default rejects unknown properties.

The validation was failing at both the client (JSON Schema validation) and server (Zod validation) levels.

[armchairdeity]

I found 2 separate issues with Zod... one is the version issue, 3.25 vs 4.x.
...

1. Schema Generation: The MCP SDK generates JSON schemas from Zod schemas using zodToJsonSchema(tool.inputSchema, { strictUnions: true, pipeStrategy: 'input' }). This creates schemas where
   nested objects implicitly have additionalProperties: false.
2. Client-side Validation: The VS Code MCP client (GitHub Copilot) adds metadata properties when invoking tools. These properties are validated against the generated schemas before the request
   is sent to the server.
3. Server-side Validation: Even if the request reaches the server, Zod validates input using .safeParseAsync(), which by default rejects unknown properties.

The validation was failing at both the client (JSON Schema validation) and server (Zod validation) levels.

Temporary Hack Solution

A two-part patch (hack) to the MCP SDK at ~/.npm/_npx/6a2bc8da53bc5e22/node_modules/@modelcontextprotocol/sdk/dist/cjs/server/mcp.js:

Part 1: Recursive Schema Modification

Added a helper function to recursively set additionalProperties: true on all object schemas:

function allowAdditionalProperties(schema) {
	if (typeof schema !== 'object' || schema === null) return schema
	if (schema.type === 'object' || schema.properties) {
		schema.additionalProperties = true
	}
	if (schema.properties) {
		for (const key in schema.properties) {
			allowAdditionalProperties(schema.properties[key])
		}
	}
	if (schema.items) {
		if (Array.isArray(schema.items)) {
			schema.items.forEach(allowAdditionalProperties)
		} else {
			allowAdditionalProperties(schema.items)
		}
	}
	if (schema.allOf) schema.allOf.forEach(allowAdditionalProperties)
	if (schema.anyOf) schema.anyOf.forEach(allowAdditionalProperties)
	if (schema.oneOf) schema.oneOf.forEach(allowAdditionalProperties)
	return schema
}

Modified schema generation (around line 65) to apply this recursively:

inputSchema: tool.inputSchema
    ? allowAdditionalProperties(Object.assign((0, zod_to_json_schema_1.zodToJsonSchema)(tool.inputSchema, {
        strictUnions: true,
        pipeStrategy: 'input'
    }), { additionalProperties: true }))
    : EMPTY_OBJECT_JSON_SCHEMA,

Part 2: Zod Validation Modification

Modified Zod validation (line 91) to use .passthrough():

// Before:
const parseResult = await tool.inputSchema.safeParseAsync(request.params.arguments)

// After:
const parseResult = await tool.inputSchema.passthrough().safeParseAsync(request.params.arguments)

The .passthrough() method tells Zod to allow and pass through unknown properties instead of rejecting them.

[christian-kreuzberger-dtx]

Hi @armchairdeity , have you had these issues with v0.13.1 of our mcp server?

[ryanfk]

@christian-kreuzberger-dtx encountered the error on:
npx --yes @dynatrace-oss/dynatrace-mcp-server@latest --version
npm warn deprecated @dynatrace-sdk/shared-client-utils@1.0.1: Deprecated
Initializing Dynatrace MCP Server v1.0.0...

[christian-kreuzberger-dtx]

@ryanfk I have tried this multiple times now, locally as well as on GitHub Codespaces, and I never ran into this issue.
My guess is that there is some cached dependency in some node_modules folder. But I can't really help with troubleshooting.