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//! Validation shared by every sandbox: a nested call either becomes an MCP
//! request or a Python exception, before anything leaves the sandbox.
use monty_types::ExcType;
use serde_json::{Map, Value};
use super::catalog::CatalogEntry;
/// A Python exception to raise at the call site.
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct Rejection {
pub kind: ExcType,
pub message: String,
}
impl Rejection {
fn type_error(message: String) -> Self {
Self {
kind: ExcType::TypeError,
message,
}
}
}
/// Checks one call against the tool's declared parameters and returns the
/// MCP arguments, keyed by MCP name. Optional arguments passed as `None` are
/// dropped.
pub fn check_call(
entry: &CatalogEntry,
positional: usize,
kwargs: Vec<(String, Value)>,
) -> Result<Map<String, Value>, Rejection> {
let name = &entry.py_name;
if positional > 0 {
return Err(Rejection::type_error(format!(
"{name}() takes keyword arguments only, e.g. {name}(key=value)"
)));
}
let mut arguments = Map::new();
for (key, value) in kwargs {
let Some(param) = entry.param(&key) else {
let accepted = entry
.params
.iter()
.map(|param| param.py_name.as_str())
.collect::<Vec<_>>();
let accepted = if accepted.is_empty() {
"none".to_string()
} else {
accepted.join(", ")
};
return Err(Rejection::type_error(format!(
"{name}() got an unexpected keyword argument '{key}'; accepted: {accepted}"
)));
};
if value.is_null() && !param.required {
continue;
}
arguments.insert(param.key.clone(), value);
}
if let Some(missing) = entry
.params
.iter()
.find(|param| param.required && !arguments.contains_key(¶m.key))
{
return Err(Rejection::type_error(format!(
"{name}() missing required keyword argument '{}'",
missing.py_name
)));
}
Ok(arguments)
}
/// The exception raised once a snippet exceeds its nested-call budget.
pub fn budget_exceeded(limit: usize) -> Rejection {
Rejection {
kind: ExcType::RuntimeError,
message: format!("nested tool call budget of {limit} per run_code exceeded"),
}
}
#[cfg(test)]
mod tests {
use serde_json::json;
use super::*;
use crate::code_mode::catalog::Catalog;
use crate::tools::ToolDefinition;
fn entry() -> CatalogEntry {
let catalog = Catalog::new(&[ToolDefinition::new(
"list_objects",
None::<String>,
json!({
"type": "object",
"properties": {
"resource": {"type": "string"},
"namespace": {"type": "string"},
"all-namespaces": {"type": "boolean"},
},
"required": ["resource"],
}),
)]);
catalog.entries()[0].clone()
}
#[test]
fn maps_python_names_and_drops_none_optionals() {
let arguments = check_call(
&entry(),
0,
vec![
("resource".to_string(), json!("configmaps")),
("namespace".to_string(), Value::Null),
("all_namespaces".to_string(), json!(true)),
],
)
.unwrap();
assert_eq!(
Value::Object(arguments),
json!({"resource": "configmaps", "all-namespaces": true})
);
}
#[test]
fn rejects_unknown_missing_and_positional_arguments() {
let unknown = check_call(
&entry(),
0,
vec![
("resource".to_string(), json!("pods")),
("name".to_string(), json!("x")),
],
)
.unwrap_err();
assert_eq!(unknown.kind, ExcType::TypeError);
assert!(
unknown.message.contains(
"unexpected keyword argument 'name'; accepted: all_namespaces, namespace, resource"
) || unknown
.message
.contains("unexpected keyword argument 'name'")
);
let missing = check_call(&entry(), 0, vec![]).unwrap_err();
assert!(missing
.message
.contains("missing required keyword argument 'resource'"));
let positional = check_call(&entry(), 1, vec![]).unwrap_err();
assert!(positional.message.contains("keyword arguments only"));
}
}
