[MCP] Support object body param and Abilities API guidance

[bgrgicak]

Motivation for the change, related issues

MCP clients (like Claude) naturally produce object values for structured parameters. Currently, callers must JSON.stringify the body before passing it to playground_request, which is an unnecessary friction point — the tool should accept both forms.

Additionally, the Abilities API (/wp-json/wp-abilities/v1/abilities) is now available and should be surfaced in the tool's guidance so MCP clients know to use it.

Implementation details

• New string_or_object param type – added to ToolParamType and handled in both the Zod schema builder (register-mcp-server-tools.ts) and the JSON Schema builder (paramsToJsonSchema in tool-definitions.ts via oneOf).
• Auto-serialization in executor – tool-executors.ts now JSON.stringifys the body when it receives an object, passing strings through unchanged.
• Updated tool description – the playground_request description now mentions the Abilities API as a first-class REST endpoint and trims redundant guidance text.

Testing Instructions

• CI

[Copilot]

Pull request overview

Adds support for passing structured (object) request bodies to the playground_request MCP tool without requiring manual JSON.stringify, and updates tool guidance to mention the Abilities API endpoint.

Changes:

• Introduces a new string_or_object parameter type and wires it through Zod + JSON Schema generation.
• Auto-serializes object bodies in the playground_request executor.
• Updates playground_request description guidance and adds an e2e test covering object body usage.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
packages/playground/mcp/tests/e2e/mcp-tools.spec.ts	Adds e2e coverage ensuring playground_request accepts object bodies.
packages/playground/mcp/src/tools/tool-executors.ts	Serializes object bodies to JSON before issuing the HTTP request.
packages/playground/mcp/src/tools/tool-definitions.ts	Adds string_or_object, updates tool guidance, and emits oneOf JSON Schema for the new type.
packages/playground/mcp/src/tools/register-mcp-server-tools.ts	Adds Zod validation support for string_or_object.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.