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| 1 | +//! `mcpmux_invoke_tool` — permission-checked gateway into backend MCP tools. |
| 2 | +
|
| 3 | +use async_trait::async_trait; |
| 4 | +use rmcp::model::{CallToolResult, Content}; |
| 5 | +use serde_json::{json, Value}; |
| 6 | + |
| 7 | +use super::registry::{MetaTool, MetaToolCall, MetaToolError}; |
| 8 | +use super::tools::{caller_resolution, caller_space_id}; |
| 9 | +use crate::pool::{format_invoke_permission_denied, format_server_inactive_error}; |
| 10 | +use crate::services::tool_discovery::ToolDiscoveryService; |
| 11 | +use mcpmux_core::FeatureType; |
| 12 | + |
| 13 | +/// Meta tool that forwards invocations to [`RoutingService::call_tool`]. |
| 14 | +pub struct InvokeToolTool; |
| 15 | + |
| 16 | +#[async_trait] |
| 17 | +impl MetaTool for InvokeToolTool { |
| 18 | + fn name(&self) -> &'static str { |
| 19 | + "mcpmux_invoke_tool" |
| 20 | + } |
| 21 | + |
| 22 | + fn description(&self) -> &'static str { |
| 23 | + "Invoke a backend MCP tool by server_id and tool name. Requires the \ |
| 24 | + server to be active (binding or session enable) and the tool to be \ |
| 25 | + in the current permission set. Use mcpmux_search_tools and \ |
| 26 | + mcpmux_get_tool_schema before calling." |
| 27 | + } |
| 28 | + |
| 29 | + fn input_schema(&self) -> Value { |
| 30 | + json!({ |
| 31 | + "type": "object", |
| 32 | + "required": ["server_id", "tool"], |
| 33 | + "properties": { |
| 34 | + "server_id": { |
| 35 | + "type": "string", |
| 36 | + "description": "Registry server id (e.g. github)" |
| 37 | + }, |
| 38 | + "tool": { |
| 39 | + "type": "string", |
| 40 | + "description": "Bare tool name on that server (e.g. list_issues), not the qualified name" |
| 41 | + }, |
| 42 | + "args": { |
| 43 | + "type": "object", |
| 44 | + "description": "Arguments object passed to the backend tool", |
| 45 | + "default": {} |
| 46 | + } |
| 47 | + } |
| 48 | + }) |
| 49 | + } |
| 50 | + |
| 51 | + fn is_write(&self) -> bool { |
| 52 | + false |
| 53 | + } |
| 54 | + |
| 55 | + async fn call(&self, call: MetaToolCall<'_>) -> Result<CallToolResult, MetaToolError> { |
| 56 | + let server_id = call |
| 57 | + .args |
| 58 | + .get("server_id") |
| 59 | + .and_then(|v| v.as_str()) |
| 60 | + .ok_or_else(|| MetaToolError::InvalidArgument("missing `server_id`".into()))? |
| 61 | + .to_string(); |
| 62 | + let tool_name = call |
| 63 | + .args |
| 64 | + .get("tool") |
| 65 | + .and_then(|v| v.as_str()) |
| 66 | + .ok_or_else(|| MetaToolError::InvalidArgument("missing `tool`".into()))? |
| 67 | + .to_string(); |
| 68 | + let args = call.args.get("args").cloned().unwrap_or_else(|| json!({})); |
| 69 | + |
| 70 | + let resolved = caller_resolution(&call).await?; |
| 71 | + let space_id = caller_space_id(&call).await?; |
| 72 | + let session_id = call.session_id; |
| 73 | + |
| 74 | + let invokable = call |
| 75 | + .ctx |
| 76 | + .feature_service |
| 77 | + .get_invokable_tools_for_grants( |
| 78 | + &space_id.to_string(), |
| 79 | + &resolved.feature_set_ids, |
| 80 | + session_id, |
| 81 | + ) |
| 82 | + .await |
| 83 | + .map_err(|e| MetaToolError::Internal(e.to_string()))?; |
| 84 | + |
| 85 | + let binding_features = call |
| 86 | + .ctx |
| 87 | + .feature_service |
| 88 | + .resolve_feature_sets(&space_id.to_string(), &resolved.feature_set_ids) |
| 89 | + .await |
| 90 | + .map_err(|e| MetaToolError::Internal(e.to_string()))?; |
| 91 | + let binding_servers: std::collections::HashSet<String> = binding_features |
| 92 | + .iter() |
| 93 | + .map(|f| f.server_id.clone()) |
| 94 | + .collect(); |
| 95 | + let session_enabled = session_id |
| 96 | + .map(|sid| call.ctx.session_overrides.enabled_set(sid)) |
| 97 | + .unwrap_or_default(); |
| 98 | + let session_disabled = session_id |
| 99 | + .map(|sid| call.ctx.session_overrides.disabled_set(sid)) |
| 100 | + .unwrap_or_default(); |
| 101 | + |
| 102 | + let is_server_active = binding_servers.contains(&server_id) |
| 103 | + || (session_enabled.contains(&server_id) && !session_disabled.contains(&server_id)); |
| 104 | + |
| 105 | + if session_disabled.contains(&server_id) { |
| 106 | + return Ok(invoke_error(format!( |
| 107 | + "server '{server_id}' is disabled for this session → mcpmux_enable_server({{ \"server_id\": \"{server_id}\" }})" |
| 108 | + ))); |
| 109 | + } |
| 110 | + |
| 111 | + if !is_server_active { |
| 112 | + return Ok(invoke_error(format_server_inactive_error(&server_id))); |
| 113 | + } |
| 114 | + |
| 115 | + let qualified_name = invokable |
| 116 | + .iter() |
| 117 | + .find(|f| f.server_id == server_id && f.feature_name == tool_name) |
| 118 | + .map(|f| f.qualified_name()) |
| 119 | + .unwrap_or_else(|| format!("{server_id}_{tool_name}")); |
| 120 | + let is_invokable = invokable.iter().any(|f| { |
| 121 | + f.feature_type == FeatureType::Tool |
| 122 | + && f.server_id == server_id |
| 123 | + && f.feature_name == tool_name |
| 124 | + && f.is_available |
| 125 | + }); |
| 126 | + |
| 127 | + if !is_invokable { |
| 128 | + let index = call |
| 129 | + .ctx |
| 130 | + .tool_discovery |
| 131 | + .build_index(&space_id.to_string(), &invokable) |
| 132 | + .await |
| 133 | + .map_err(|e| MetaToolError::Internal(e.to_string()))?; |
| 134 | + let suggestions: Vec<String> = ToolDiscoveryService::search( |
| 135 | + &index, |
| 136 | + Some(&tool_name), |
| 137 | + Some(&server_id), |
| 138 | + crate::services::tool_discovery::DetailLevel::Name, |
| 139 | + 5, |
| 140 | + None, |
| 141 | + ) |
| 142 | + .tools |
| 143 | + .iter() |
| 144 | + .filter_map(|v| { |
| 145 | + v.get("qualified_name") |
| 146 | + .and_then(|n| n.as_str().map(String::from)) |
| 147 | + }) |
| 148 | + .collect(); |
| 149 | + return Ok(invoke_error(format_invoke_permission_denied( |
| 150 | + &qualified_name, |
| 151 | + &server_id, |
| 152 | + &tool_name, |
| 153 | + &suggestions, |
| 154 | + ))); |
| 155 | + } |
| 156 | + |
| 157 | + let routing = call |
| 158 | + .ctx |
| 159 | + .routing_service |
| 160 | + .as_ref() |
| 161 | + .ok_or_else(|| MetaToolError::Internal("invoke routing not configured".into()))?; |
| 162 | + match routing |
| 163 | + .call_tool( |
| 164 | + space_id, |
| 165 | + &resolved.feature_set_ids, |
| 166 | + session_id, |
| 167 | + &qualified_name, |
| 168 | + args, |
| 169 | + ) |
| 170 | + .await |
| 171 | + { |
| 172 | + Ok(result) => { |
| 173 | + let content: Vec<Content> = result |
| 174 | + .content |
| 175 | + .into_iter() |
| 176 | + .filter_map(|v| serde_json::from_value(v).ok()) |
| 177 | + .collect(); |
| 178 | + let mut mcp_result = if result.is_error { |
| 179 | + CallToolResult::error(content) |
| 180 | + } else { |
| 181 | + CallToolResult::success(content) |
| 182 | + }; |
| 183 | + mcp_result.structured_content = result.structured_content; |
| 184 | + Ok(mcp_result) |
| 185 | + } |
| 186 | + Err(e) => Ok(invoke_error(e.to_string())), |
| 187 | + } |
| 188 | + } |
| 189 | +} |
| 190 | + |
| 191 | +/// Build a structured MCP error payload for invoke failures. |
| 192 | +fn invoke_error(message: String) -> CallToolResult { |
| 193 | + let payload = json!({ |
| 194 | + "error": "invoke_failed", |
| 195 | + "message": message, |
| 196 | + }); |
| 197 | + CallToolResult::error(vec![Content::text(payload.to_string())]) |
| 198 | +} |
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