Complete MCP validation, defaults, and self-correction

[sebawebber]

Parent

#43

What to build

Complete the MCP Tuning Request contract so an AI agent can safely normalize a
valid request, expose every fallback as a Tuning Assumption, and self-correct
missing or invalid facts from actionable tool execution errors.

Acceptance criteria

• total_ram, total_cpu, and postgres_version are required and missing values return actionable MCP tool execution errors rather than transport errors.
• Total RAM accepts a positive integer with a mandatory case-insensitive B, KB, MB, GB, or TB unit; decimals, missing units, unknown units, zero, and negative values are rejected.
• Total CPU accepts only a positive integer representing logical CPUs.
• PostgreSQL Version remains a dotted numeric string, preserves the complete supplied value, derives PostgreSQL Major Version using PostgreSQL policy, and supports 9.1–9.6 and 10–18.
• PostgreSQL Version syntax and supported major series are validated without attempting to validate the exact minor-release catalog.
• Profile, disk type, operating system, architecture aliases, and maximum connections are normalized according to the parent specification.
• Omitted optional fields use WEB, SSD, linux, amd64, and 100 respectively, with every fallback exposed as a Tuning Assumption.
• Invalid optional values are rejected instead of silently receiving defaults.
• Warnings are represented separately from Tuning Assumptions and do not turn a usable result into an error.
• The normalized request echoes every supplied or defaulted field.
• Table-driven domain tests and MCP handler tests cover valid variants, defaults, aliases, boundary values, and actionable errors.

Blocked by

• Serve a happy-path MCP tuning recommendation #45