[MCP SDK] ToolCallHandler now returns structuredContent if applicable

[xavierleune]

Q	A
Bug fix?	no
New feature?	yes
Docs?	no
Issues	Fix #...
License	MIT

As per documentation we should include any structured content in a dedicated field

Structured content is returned as a JSON object in the structuredContent field of a result.
For backwards compatibility, a tool that returns structured content SHOULD also return the serialized JSON in a TextContent block.

[JoshuaBehrens]

I have a similar patch in local testing :)

[OskarStark]

Please rebase, thanks

[xavierleune]

@OskarStark done 👍

[chr-hertel]

Two things, I think this is good timing to add a test for checking the two options for type text.

Isn't it that with the current approach we end up with something like "text": "\"foobar\"" for simple, unstructured text values?

[OskarStark]

Open to finish this PR @xavierleune ?

[Copilot]

Pull Request Overview

This PR implements structured content support in the MCP SDK's ToolCallHandler to comply with the MCP specification. The change allows tools to return structured data (arrays/objects) which will be included in both the structuredContent field and serialized as JSON in the text content for backwards compatibility.

• Modified ToolCallResult to accept mixed data types instead of strings only
• Updated ToolCallHandler to detect structured content and include it in the structuredContent field
• Fixed a typo in the default MIME type from "text/plan" to "text/plain"

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/mcp-sdk/src/Capability/Tool/ToolCallResult.php	Changed result property from string to mixed type and fixed MIME type typo
src/mcp-sdk/src/Server/RequestHandler/ToolCallHandler.php	Added structured content detection and JSON encoding with proper error handling

[Copilot]

The operator precedence is incorrect. The condition should be grouped as ('text' === $result->type) && (\is_array($result->result) || \is_object($result->result)) to ensure structured content is only added for text type results.

Suggested change

	if ('text' === $result->type && \is_array($result->result) || \is_object($result->result)) {
	if ('text' === $result->type && (\is_array($result->result) || \is_object($result->result))) {