ADR-010: Tool/Function Calling Design 

Status 

Accepted (2024-04)

Context 

Modern LLMs support tool/function calling for:

  • External data retrieval.
  • Action execution.
  • Structured output generation.

Decision 

Support OpenAI-compatible tool format:

Example: Tool definition 
$tools = [
    [
        'type' => 'function',
        'function' => [
            'name' => 'get_weather',
            'description' => 'Get weather for location',
            'parameters' => [
                'type' => 'object',
                'properties' => [
                    'location' => ['type' => 'string'],
                ],
                'required' => ['location'],
            ],
        ],
    ],
];
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Tool calls returned in CompletionResponse::$toolCalls:

  • A typed list<ToolCall> (nullable) of ToolCall value objects — each with the tool id, name and its arguments as an already JSON-decoded associative array (not an encoded string). A full tool-execution runtime was added later in ADR-038.

Consequences 

Positive:

  • ●● Industry-standard format.
  • ●● Cross-provider compatibility.
  • ● Flexible tool definitions.
  • ● Type-safe parameters.

Negative:

  • ◑ Complex nested structure.
  • ◑ Provider translation needed.
  • ✕ No automatic execution.
  • ◑ Testing complexity.

Net Score: +5.0 (Positive impact - OpenAI-compatible format ensures broad compatibility)