harn-vm 0.8.3

Async bytecode virtual machine for the Harn programming language
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128

use crate::value::{VmError, VmValue};

use super::convert::{annotations_to_json, vm_value_to_json};
use super::defs::McpToolDef;

/// Extract tools from a Harn tool_registry VmValue and convert to MCP tool definitions.
pub fn tool_registry_to_mcp_tools(registry: &VmValue) -> Result<Vec<McpToolDef>, VmError> {
    let dict = match registry {
        VmValue::Dict(d) => d,
        _ => {
            return Err(VmError::Runtime(
                "mcp_tools: argument must be a tool registry".into(),
            ));
        }
    };

    match dict.get("_type") {
        Some(VmValue::String(t)) if &**t == "tool_registry" => {}
        _ => {
            return Err(VmError::Runtime(
                "mcp_tools: argument must be a tool registry (created with tool_registry())".into(),
            ));
        }
    }

    let tools = match dict.get("tools") {
        Some(VmValue::List(list)) => list,
        _ => return Ok(Vec::new()),
    };

    let mut mcp_tools = Vec::new();
    for tool in tools.iter() {
        if let VmValue::Dict(entry) = tool {
            let name = entry.get("name").map(|v| v.display()).unwrap_or_default();
            let title = entry.get("title").map(|v| v.display());
            let description = entry
                .get("description")
                .map(|v| v.display())
                .unwrap_or_default();

            let handler = match entry.get("handler") {
                Some(VmValue::Closure(c)) => (**c).clone(),
                _ => {
                    return Err(VmError::Runtime(format!(
                        "mcp_tools: tool '{name}' has no handler closure"
                    )));
                }
            };

            let input_schema = params_to_json_schema(entry.get("parameters"));
            let output_schema = entry.get("outputSchema").and_then(|v| {
                if let VmValue::Dict(_) = v {
                    Some(vm_value_to_json(v))
                } else {
                    None
                }
            });
            let annotations = entry.get("annotations").and_then(annotations_to_json);
            let icons = entry.get("icons").and_then(|v| {
                if let VmValue::List(_) = v {
                    Some(vm_value_to_json(v))
                } else {
                    None
                }
            });

            mcp_tools.push(McpToolDef {
                name,
                title,
                description,
                input_schema,
                output_schema,
                annotations,
                icons,
                handler,
            });
        }
    }

    Ok(mcp_tools)
}

/// Convert Harn tool_define parameter definitions to JSON Schema for MCP inputSchema.
pub(super) fn params_to_json_schema(params: Option<&VmValue>) -> serde_json::Value {
    let params_dict = match params {
        Some(VmValue::Dict(d)) => d,
        _ => {
            return serde_json::json!({ "type": "object", "properties": {} });
        }
    };

    let mut properties = serde_json::Map::new();
    let mut required = Vec::new();

    for (param_name, param_def) in params_dict.iter() {
        if let VmValue::Dict(def) = param_def {
            let mut prop = serde_json::Map::new();
            if let Some(VmValue::String(t)) = def.get("type") {
                prop.insert("type".into(), serde_json::Value::String(t.to_string()));
            }
            if let Some(VmValue::String(d)) = def.get("description") {
                prop.insert(
                    "description".into(),
                    serde_json::Value::String(d.to_string()),
                );
            }
            if matches!(def.get("required"), Some(VmValue::Bool(true))) {
                required.push(serde_json::Value::String(param_name.clone()));
            }
            properties.insert(param_name.clone(), serde_json::Value::Object(prop));
        } else if let VmValue::String(type_str) = param_def {
            let mut prop = serde_json::Map::new();
            prop.insert(
                "type".into(),
                serde_json::Value::String(type_str.to_string()),
            );
            properties.insert(param_name.clone(), serde_json::Value::Object(prop));
        }
    }

    let mut schema = serde_json::Map::new();
    schema.insert("type".into(), serde_json::Value::String("object".into()));
    schema.insert("properties".into(), serde_json::Value::Object(properties));
    if !required.is_empty() {
        schema.insert("required".into(), serde_json::Value::Array(required));
    }
    serde_json::Value::Object(schema)
}