Definition: "I can parse what you wrote, but it doesn't make sense" - violations of meaning or contracts within a correctly structured format. The parser successfully extracts function calls, but they violate tool contracts or constraints.
Characteristics:
- Structure (syntax) is valid but violates the tool's interface specification
- Parser can extract the function call
- Validation against tool definition fails
- There exists a potential tool definition that would make this call valid but it is not the one that is in the system prompt
Tool resolution failed - the specified tool name doesn't exist or isn't accessible.
Tool name not recognized in the system.
Example:
<function_calls>
<invoke name="get_weather_info"> <!-- Function doesn't exist -->
<parameter name="location">["San Francisco", "CA"]</parameter>
</invoke>
</function_calls>Current implementation mapping: BadArgumentOrName + "Unrecognized tool name" → Penalty: FCUReactorInvalidToolName
Tool exists but not accessible in current context.
What it is: Occurs when the model tries to call a tool that exists in the system but is marked as is_externally_callable=False. These tools are hidden from the system prompt and are typically internal "meta tools" meant to be called only by other tools, not directly by the model.
Why it's penalized: The model is calling a tool it was never told about (filtered out of system prompt), indicating it's either hallucinating tool names or trying to guess hidden functionality.
Current implementation mapping: BadArgumentOrName + "not externally callable" → Penalty: FCUReactorInvalidToolName
A parameter marked as required in the tool definition is not provided.
Examples (assuming 'location' is required for get_current_weather, 'to' is required for send_email):
<!-- Missing 'to' parameter for send_email -->
<function_calls>
<invoke name="send_email">
<parameter name="subject">Weather Alert</parameter>
<parameter name="body">It might rain!</parameter>
<!-- Missing required "to" parameter -->
</invoke>
</function_calls>Current implementation mapping: BadArgumentOrName + "Missing required parameter {param.name}" → Penalty: FCUReactorInvalidToolName
Parameter name provided doesn't exist in the tool definition.
Examples:
<!-- Wrong parameter name: 'place' instead of 'location' -->
<function_calls>
<invoke name="get_current_weather">
<parameter name="place">["San Francisco", "CA"]</parameter>
<parameter name="units">fahrenheit</parameter>
</invoke>
</function_calls>Current implementation mapping: BadArgumentOrName + "Unknown parameter {param_name}" → Penalty: FCUReactorInvalidToolName
Parameter value fails validation against the tool's schema.
Value is of wrong JSON type (e.g., string instead of number).
Example (assuming 'location' must be an array):
<function_calls>
<invoke name="get_current_weather">
<parameter name="location">San Francisco</parameter> <!-- Should be array -->
</invoke>
</function_calls>Current implementation mapping: BadArgumentOrName + "does not match type={param.schema_str}" → Penalty: FCUReactorInvalidToolName
Wrong object shape - missing required properties or extra properties not allowed.
Current implementation mapping: BadArgumentOrName + "does not match type={param.schema_str}" → Penalty: FCUReactorInvalidToolName
Right type/structure but value violates constraints. This is a conceptual grouping that encompasses:
- OutOfRange: Number outside allowed range (min/max)
- InvalidLength: String or array length violation (minLength/maxLength)
- PatternMismatch: String doesn't match required regex pattern
- InvalidOption: Value not in allowed enumeration
Example (assuming 'units' must be 'celsius' or 'fahrenheit'):
<function_calls>
<invoke name="get_current_weather">
<parameter name="location">["San Francisco", "CA"]</parameter>
<parameter name="units">kelvin</parameter> <!-- Not in enum [celsius, fahrenheit] -->
</invoke>
</function_calls>Current implementation mapping: BadArgumentOrName + "does not match type={param.schema_str}" → Penalty: FCUReactorInvalidToolName