Proposal: support configuration-defined prompts in mcp-server

Related issue

#4181

Motivation

The MCP server plugin supports exposing tools, but does not currently support configuration-defined prompts through prompts/list and prompts/get.

Users should be able to expose reusable prompt definitions alongside their tools without implementing a separate MCP server.

Proposed scope

Add configuration-defined prompts to the MCP server plugin, including:

• A name and optional description.
• Named string arguments, with optional descriptions and required flags.
• Text messages whose content can reference the declared arguments.
• prompts/list to list available prompt definitions.
• prompts/get to retrieve a prompt with supplied arguments.
• Capability reporting consistent with the prompts available on the endpoint.

The Design will specify the configuration schema, argument substitution rules, and supported protocol versions before implementation begins.

Out of scope

• Higress Console changes.
• Remote prompt registries or runtime prompt-management APIs.
• Workflow execution or LLM invocation.
• Image, audio, and embedded-resource prompt content.
• Prompt change notifications.

Acceptance criteria

• A configured prompt can be listed and retrieved with valid arguments.
• Unknown prompt names, missing required arguments, and invalid argument types return appropriate protocol errors.
• Invalid prompt configuration is reported through the existing configuration-validation mechanism.
• Prompt configuration remains isolated between server configurations, including configuration reloads.
• Existing tool behavior and endpoints without prompt configuration remain unchanged.
• Tests cover the supported protocol versions, capability reporting, argument handling, and existing tool functionality.
• Runtime verification demonstrates prompt discovery and retrieval through the gateway.

Coordination

I would like to work on this if no implementation is already underway.

Could maintainers confirm whether this initial scope is acceptable and whether it overlaps with any planned work? After scope approval, I will prepare a linked Design with the implementation approach and verification plan.

AI assistance

AI has assisted with repository investigation and preparation of this proposal. Implementation and testing are also expected to use AI assistance, with human review.

No implementation changes have been made for this proposal. Implementation will begin after maintainer approval of both the Proposal and the linked Design.