Translator only unwrapped tool.function when both tool.type==="function"
and tool.function were truthy. Loose/legacy OpenAI clients emit the bare
{ function: { name, parameters } } shape (no parent type), which fell
through and forwarded name: undefined upstream, rejected by strict
Anthropic-compatible gateways (MiniMax M3) as (2013) invalid tool type.
Unwrap tool.function whenever present. Built-in tools stay pass-through.
Adds regression coverage for the 4 tool shapes. See #2435.
Co-authored-by: Cursor <cursoragent@cursor.com>
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