alonf/mcppythondemo/python-mcp-elicitation

Python MCP Elicitation Skill

Use When

You need a Python MCP server/client pair to support safe server-driven form elicitation, especially for risky actions like process termination.

Pattern

1. Server tool

• Accept Context in the tool signature.
• Check client capability with ctx.request_context.session.check_client_capability(...).
• If dynamic form options are needed, call ctx.request_context.session.elicit_form(...) with a hand-built restricted JSON schema instead of relying on static Pydantic models.

1. Selection step

• Build a single top-level field with oneOf options:
• const: machine-readable value (PID, identifier, etc.)
• title: human-readable label for the client UI
• Keep the form flat; MCP elicitation schemas are intentionally simple.

1. Confirmation step

• Always require a typed phrase for destructive actions.
• Validate exact phrase match server-side, but compare case-insensitively for usability.

1. Lecture/demo client

• Pass elicitation_callback= to ClientSession(...) only when local interaction is actually possible (stdin/stdout are TTYs).
• In the callback, support:
• single-field oneOf/enum selection forms
• single-field text prompts
• Return ElicitResult(action="cancel") on blank input so the server can treat it as a safe cancel.

1. Linux process termination

• Prefer SIGTERM first, then SIGKILL after a short timeout.
• Treat zombie processes as exited in /proc/<pid>/stat to avoid hanging on child processes owned by another parent.

Reference Files

• src/mcp_linux_diag_server/tools/processes.py
• src/mcp_linux_diag_server/server.py
• src/mcp_linux_diag_server/client.py
• tests/test_processes.py
• tests/test_m5_http.py

QA Pattern

• For integration tests, use a schema-driven callback that inspects the single elicited field and auto-fills:
• matching oneOf / enum path options when present
• True for boolean approvals
• quoted confirmation phrases when the schema description demands exact text
• the requested path or a stable QA reason for free-text fields
• This keeps access/approval tests reusable even when the server changes the exact elicitation schema shape but preserves the single-field MCP form contract.