met 1.0.0-beta-preview

Metrale Engine: pure Rust LLM inference server (HTTP API, scheduler, TUI, CLI).
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// SPDX-License-Identifier: MIT OR Apache-2.0
#![allow(unused_imports, dead_code)]

//! 2026-09-26: The Hermes tool-call format.
//!
//! Owner: server (tool parsing).
//! Invariants: none beyond the types.

use super::*;

/// 2026-09-26: Hermes format: JSON `{"name":"fn","arguments":{...}}` inside
/// `<tool_call>` tags.
pub struct HermesParser;

impl ToolCallParser for HermesParser {
    fn name(&self) -> &str {
        "hermes"
    }

    fn compile_tool_grammar(
        &self,
        engine: &mut GrammarEngine,
        tools: &[ToolDefinition],
        use_triggers: bool,
    ) -> Option<Result<CompiledGrammar, GrammarError>> {
        Some(engine.compile_hermes_tool_grammar(tools, use_triggers))
    }

    fn has_tool_grammar(&self) -> bool {
        true
    }

    fn system_prompt(
        &self,
        tools: &[ToolDefinition],
        tool_choice: &ToolChoice,
        levers: &super::PromptLevers,
    ) -> String {
        let tools_json = tool_list_body(tools, levers, || {
            serde_json::to_string(tools).unwrap_or_else(|_| "[]".into())
        });
        let mut prompt = format!(
            "You are a function calling AI model. You are provided with function signatures within \
             <tools></tools> XML tags. You may call one or more functions to assist with the user \
             query. Don't make assumptions about what values to plug into functions. Here are the \
             available tools:\n<tools>\n{tools_json}\n</tools>\n\n\
             For each function call, return a JSON object with function name and arguments within \
             <tool_call></tool_call> XML tags:\n<tool_call>\n\
             {{\"name\": <function-name>, \"arguments\": <args-json-object>}}\n</tool_call>"
        );
        append_tool_choice_instruction(&mut prompt, tool_choice);
        prompt
    }

    fn format_tool_calls(&self, calls: &[IncomingToolCall]) -> String {
        let mut out = String::new();
        for tc in calls {
            let args: serde_json::Value = serde_json::from_str(&tc.function.arguments)
                .unwrap_or(serde_json::Value::Object(Default::default()));
            out.push_str(&format!(
                "\n<tool_call>\n{}\n</tool_call>",
                serde_json::json!({"name": tc.function.name, "arguments": args})
            ));
        }
        out
    }
}