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A call to a custom (freeform-grammar) tool created by the model — distinct from function_call. Used for tools like Codex CLI’s apply_patch whose payload is opaque text rather than JSON arguments.

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Fields

FieldTypeRequiredDescription
CallIDstring:heavy_check_mark:N/A
ID*string:heavy_minus_sign:N/A
Inputstring:heavy_check_mark:N/A
Namestring:heavy_check_mark:N/A
Namespace*string:heavy_minus_sign:Namespace qualifier for tools registered as part of a namespace tool group (e.g. an MCP server)
Typecomponents.CustomToolCallItemType:heavy_check_mark:N/A