Validate tool call arguments against each tool's Parameters() JSON Schema
in ExecuteWithContext() before calling Execute(). This prevents type
confusion, argument injection, and missing-field errors from reaching tools.
Validates: required fields, type matching (string/integer/number/boolean/
array/object), enum membership, nested objects (recursive), array element
types. Rejects unexpected extra properties unless additionalProperties is
set to true (for MCP tool compatibility).
Returns ToolResult{IsError: true} on failure so the LLM can self-correct.
Ref: Security Hardening > Tool abuse prevention via strict parameter validation
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