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feat(mcp): route shell as built-in MCP tool (PR 1 of 2) #1424

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2f1dd2e
feat(mcp): route shell as built-in MCP tool
RohanSogani May 1, 2026
3b9cdbe
address review comments
RohanSogani May 1, 2026
cf8cbf9
address review comments 2
RohanSogani May 1, 2026
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16 changes: 16 additions & 0 deletions crates/mcp/src/core/config.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -304,6 +304,8 @@ pub enum BuiltinToolType {
FileSearch,
/// Image generation tool (OpenAI: image_generation)
ImageGeneration,
/// Shell tool (OpenAI: shell)
Shell,
}

impl BuiltinToolType {
Expand All @@ -314,6 +316,7 @@ impl BuiltinToolType {
BuiltinToolType::CodeInterpreter => ResponseFormatConfig::CodeInterpreterCall,
BuiltinToolType::FileSearch => ResponseFormatConfig::FileSearchCall,
BuiltinToolType::ImageGeneration => ResponseFormatConfig::ImageGenerationCall,
BuiltinToolType::Shell => ResponseFormatConfig::ShellCall,
}
}
}
Expand All @@ -325,6 +328,7 @@ impl fmt::Display for BuiltinToolType {
BuiltinToolType::CodeInterpreter => write!(f, "code_interpreter"),
BuiltinToolType::FileSearch => write!(f, "file_search"),
BuiltinToolType::ImageGeneration => write!(f, "image_generation"),
BuiltinToolType::Shell => write!(f, "shell"),
}
}
}
Expand Down Expand Up @@ -355,6 +359,7 @@ pub enum ResponseFormatConfig {
CodeInterpreterCall,
FileSearchCall,
ImageGenerationCall,
ShellCall,
}

/// Argument mapping configuration for tool aliases.
Expand Down Expand Up @@ -1034,6 +1039,7 @@ tools:
ResponseFormatConfig::ImageGenerationCall,
"\"image_generation_call\"",
),
(ResponseFormatConfig::ShellCall, "\"shell_call\""),
];

for (format, expected) in formats {
Expand Down Expand Up @@ -1201,6 +1207,7 @@ policy:
(BuiltinToolType::CodeInterpreter, "\"code_interpreter\""),
(BuiltinToolType::FileSearch, "\"file_search\""),
(BuiltinToolType::ImageGeneration, "\"image_generation\""),
(BuiltinToolType::Shell, "\"shell\""),
];

for (builtin_type, expected) in types {
Expand Down Expand Up @@ -1230,6 +1237,10 @@ policy:
BuiltinToolType::ImageGeneration.response_format(),
ResponseFormatConfig::ImageGenerationCall
);
assert_eq!(
BuiltinToolType::Shell.response_format(),
ResponseFormatConfig::ShellCall
);
}

#[test]
Expand Down Expand Up @@ -1522,5 +1533,10 @@ servers:
"code_interpreter"
);
assert_eq!(BuiltinToolType::FileSearch.to_string(), "file_search");
assert_eq!(
BuiltinToolType::ImageGeneration.to_string(),
"image_generation"
);
assert_eq!(BuiltinToolType::Shell.to_string(), "shell");
}
}
1 change: 1 addition & 0 deletions crates/mcp/src/core/session.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -864,6 +864,7 @@ impl<'a> McpToolSession<'a> {
BuiltinToolType::WebSearchPreview,
BuiltinToolType::CodeInterpreter,
BuiltinToolType::FileSearch,
BuiltinToolType::Shell,
Comment thread
RohanSogani marked this conversation as resolved.
]
.into_iter()
.filter_map(|builtin_type| orchestrator.find_builtin_server(builtin_type))
Expand Down
117 changes: 115 additions & 2 deletions crates/mcp/src/transform/transformer.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,8 +2,8 @@

use openai_protocol::responses::{
CodeInterpreterCallStatus, CodeInterpreterOutput, FileSearchCallStatus, FileSearchResult,
ImageGenerationCallStatus, ResponseOutputItem, WebSearchAction, WebSearchCallStatus,
WebSearchSource,
ImageGenerationCallStatus, ResponseOutputItem, ShellCallAction, ShellCallStatus,
WebSearchAction, WebSearchCallStatus, WebSearchSource,
};
use tracing::warn;

Expand Down Expand Up @@ -101,6 +101,7 @@ impl ResponseTransformer {
ResponseFormat::ImageGenerationCall => {
Self::to_image_generation_call(result, tool_call_id)
}
ResponseFormat::ShellCall => Self::to_shell_call(tool_call_id, arguments),
}
}

Expand Down Expand Up @@ -586,6 +587,54 @@ impl ResponseTransformer {
attributes: None,
})
}

/// Transform to shell_call output.
fn to_shell_call(tool_call_id: &str, arguments: &str) -> ResponseOutputItem {
let action = parse_shell_call_action(arguments);

ResponseOutputItem::ShellCall {
id: normalize_shell_call_id(tool_call_id),
call_id: tool_call_id.to_string(),
action,
environment: None,
status: ShellCallStatus::Completed,
created_by: None,
}
}
}

fn parse_shell_call_action(arguments: &str) -> ShellCallAction {
let Ok(value) = serde_json::from_str::<serde_json::Value>(arguments) else {
warn!("Failed to parse shell_call arguments as JSON; emitting empty action");
return empty_shell_call_action();
};

let Some(object) = value.as_object() else {
warn!("Expected shell_call arguments to be a JSON object; emitting empty action");
return empty_shell_call_action();
};

let action = serde_json::json!({
"commands": object.get("commands").cloned().unwrap_or_else(|| serde_json::json!([])),
"max_output_length": object.get("max_output_length").cloned().unwrap_or(serde_json::Value::Null),
"timeout_ms": object.get("timeout_ms").cloned().unwrap_or(serde_json::Value::Null),
});

serde_json::from_value::<ShellCallAction>(action).unwrap_or_else(|e| {
warn!(
error = %e,
"Failed to parse shell_call action fields; emitting empty action"
);
empty_shell_call_action()
})
}

fn empty_shell_call_action() -> ShellCallAction {
ShellCallAction {
commands: Vec::new(),
max_output_length: None,
timeout_ms: None,
}
}

/// Strip the base64 `result` payload from an `ImageGenerationCall` output
Expand Down Expand Up @@ -633,6 +682,18 @@ fn parse_text_block_payload(item: &serde_json::Value) -> Option<serde_json::Valu
}
}

fn normalize_shell_call_id(source_id: &str) -> String {
if source_id.starts_with("sc_") {
return source_id.to_string();
}

source_id
.strip_prefix("fc_")
.or_else(|| source_id.strip_prefix("call_"))
.map(|stripped| format!("sc_{stripped}"))
.unwrap_or_else(|| format!("sc_{source_id}"))
}

#[cfg(test)]
mod tests {
use serde_json::json;
Expand Down Expand Up @@ -1022,6 +1083,58 @@ mod tests {
}
}

#[test]
fn test_shell_call_transform() {
let transformed = ResponseTransformer::transform(
&json!({}),
&ResponseFormat::ShellCall,
"call-shell-1",
"server",
"shell",
r#"{"commands":["echo hello"],"timeout_ms":1000}"#,
);

match transformed {
ResponseOutputItem::ShellCall {
id,
call_id,
action,
environment,
status,
..
} => {
assert_eq!(id, "sc_call-shell-1");
assert_eq!(call_id, "call-shell-1");
assert_eq!(action.commands, vec!["echo hello"]);
assert_eq!(action.timeout_ms, Some(1000));
assert!(environment.is_none());
assert_eq!(status, ShellCallStatus::Completed);
}
_ => panic!("Expected ShellCall"),
}
}

#[test]
fn test_shell_call_transform_preserves_action_with_dispatch_metadata() {
let transformed = ResponseTransformer::transform(
&json!({}),
&ResponseFormat::ShellCall,
"call-shell-2",
"server",
"shell",
r#"{"commands":["pwd"],"timeout_ms":500,"user":"request-user"}"#,
);

match transformed {
ResponseOutputItem::ShellCall { action, .. } => {
assert_eq!(action.commands, vec!["pwd"]);
assert_eq!(action.timeout_ms, Some(500));
assert_eq!(action.max_output_length, None);
}
_ => panic!("Expected ShellCall"),
}
}

#[test]
fn test_file_search_transform() {
let result = json!({
Expand Down
6 changes: 6 additions & 0 deletions crates/mcp/src/transform/types.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,8 @@ pub enum ResponseFormat {
FileSearchCall,
/// Transform to OpenAI image_generation_call format
ImageGenerationCall,
/// Transform to OpenAI shell_call format
ShellCall,
}

impl ResponseFormat {
Expand All @@ -36,6 +38,7 @@ impl ResponseFormat {
ResponseFormat::CodeInterpreterCall => Some(BuiltinToolType::CodeInterpreter),
ResponseFormat::FileSearchCall => Some(BuiltinToolType::FileSearch),
ResponseFormat::ImageGenerationCall => Some(BuiltinToolType::ImageGeneration),
ResponseFormat::ShellCall => Some(BuiltinToolType::Shell),
}
}
}
Expand All @@ -48,6 +51,7 @@ impl From<ResponseFormatConfig> for ResponseFormat {
ResponseFormatConfig::CodeInterpreterCall => ResponseFormat::CodeInterpreterCall,
ResponseFormatConfig::FileSearchCall => ResponseFormat::FileSearchCall,
ResponseFormatConfig::ImageGenerationCall => ResponseFormat::ImageGenerationCall,
ResponseFormatConfig::ShellCall => ResponseFormat::ShellCall,
}
}
}
Expand All @@ -70,6 +74,7 @@ mod tests {
ResponseFormat::ImageGenerationCall,
"\"image_generation_call\"",
),
(ResponseFormat::ShellCall, "\"shell_call\""),
];

for (format, expected) in formats {
Expand All @@ -95,6 +100,7 @@ mod tests {
BuiltinToolType::CodeInterpreter,
BuiltinToolType::FileSearch,
BuiltinToolType::ImageGeneration,
BuiltinToolType::Shell,
];
for kind in kinds {
let fmt: ResponseFormat = kind.response_format().into();
Expand Down
49 changes: 48 additions & 1 deletion model_gateway/src/routers/common/mcp_utils.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -188,6 +188,7 @@ pub fn collect_builtin_routing(
ResponseTool::WebSearchPreview(_) => BuiltinToolType::WebSearchPreview,
ResponseTool::CodeInterpreter(_) => BuiltinToolType::CodeInterpreter,
ResponseTool::ImageGeneration(_) => BuiltinToolType::ImageGeneration,
ResponseTool::Shell(_) => BuiltinToolType::Shell,
Comment thread
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_ => continue,
};

Expand Down Expand Up @@ -229,6 +230,7 @@ pub fn extract_builtin_types(tools: &[ResponseTool]) -> Vec<BuiltinToolType> {
ResponseTool::WebSearchPreview(_) => Some(BuiltinToolType::WebSearchPreview),
ResponseTool::CodeInterpreter(_) => Some(BuiltinToolType::CodeInterpreter),
ResponseTool::ImageGeneration(_) => Some(BuiltinToolType::ImageGeneration),
ResponseTool::Shell(_) => Some(BuiltinToolType::Shell),
Comment thread
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_ => None,
})
.collect()
Expand Down Expand Up @@ -414,7 +416,7 @@ mod tests {
common::Function,
responses::{
CodeInterpreterTool, FunctionTool, ImageGenerationTool, McpTool, ResponseTool,
WebSearchPreviewTool,
ShellTool, WebSearchPreviewTool,
},
};
use serde_json::json;
Expand Down Expand Up @@ -699,6 +701,51 @@ mod tests {
);
}

#[tokio::test]
async fn test_collect_builtin_routing_shell() {
let mut shell_tools = HashMap::new();
shell_tools.insert(
"execute_shell_commands".to_string(),
ToolConfig {
response_format: ResponseFormatConfig::ShellCall,
..Default::default()
},
);

let config = McpConfig {
servers: vec![McpServerConfig {
name: "shell-server".to_string(),
transport: McpTransport::Streamable {
url: "http://localhost:9996/shell".to_string(),
token: None,
headers: HashMap::new(),
},
proxy: None,
required: false,
tools: Some(shell_tools),
builtin_type: Some(BuiltinToolType::Shell),
builtin_tool_name: Some("execute_shell_commands".to_string()),
internal: false,
}],
pool: Default::default(),
proxy: None,
warmup: Vec::new(),
inventory: Default::default(),
policy: Default::default(),
};

let orchestrator = Arc::new(McpOrchestrator::new(config).await.unwrap());
let tools = vec![ResponseTool::Shell(ShellTool::default())];

let routing = collect_builtin_routing(&orchestrator, Some(&tools));

assert_eq!(routing.len(), 1);
assert_eq!(routing[0].builtin_type, BuiltinToolType::Shell);
assert_eq!(routing[0].server_name, "shell-server");
assert_eq!(routing[0].tool_name, "execute_shell_commands");
assert_eq!(routing[0].response_format, ResponseFormat::ShellCall);
}

// =========================================================================
// ensure_request_mcp_client tests
// =========================================================================
Expand Down
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