Fix tool to open Apollo Explorer

Author: pubmodmatt

Cargo.lock

@@ -6,6 +6,12 @@ package.version = "0.1.0"
 
 [workspace.dependencies]
 apollo-compiler = "1.27.0"
+insta = { version = "1.43.1", features = [
+    "json",
+    "redactions",
+    "yaml",
+    "glob",
+] }
 serde = { version = "1.0.219", features = ["derive"] }
 serde_json = "1.0.140"
 thiserror = "2.0.12"

Cargo.toml

@@ -34,10 +34,9 @@ tracing.workspace = true
 tracing-subscriber = { version = "0.3.19", features = ["env-filter"] }
 regex = "1.11.1"
 webbrowser = "1.0.4"
-base64 = "0.22.1"
 
 [dev-dependencies]
-insta = "1.42.2"
+insta = { workspace = true }
 
 [lints]
 workspace = true

crates/mcp-apollo-server/Cargo.toml

@@ -1,11 +1,11 @@
 use crate::errors::McpError;
 use crate::schema_from_type;
-use base64::Engine;
 use rmcp::model::{CallToolResult, Content, ErrorCode, Tool};
 use rmcp::schemars::JsonSchema;
 use rmcp::serde_json::Value;
 use rmcp::{schemars, serde_json};
 use serde::Deserialize;
+use tracing::info;
 
 pub(crate) const EXPLORER_TOOL_NAME: &str = "explorer";
 
@@ -36,24 +36,77 @@ impl Explorer {
             variant,
             tool: Tool::new(
                 EXPLORER_TOOL_NAME,
-                "Open a GraphQL operation in Apollo Explorer",
+                "Open a GraphQL operation in Apollo Explorer. The input fields must be in the order document, variables, headers. All fields must be present, but if they are not set, set them to a string containing just `{}`",
                 schema_from_type!(Input),
             ),
         }
     }
 
     fn create_explorer_url(&self, input: &Value) -> String {
-        let compressed = lz_str::compress_to_uint8_array(input.to_string().as_str());
-        let encoded = base64::engine::general_purpose::STANDARD.encode(compressed);
+        let compressed = lz_str::compress_to_encoded_uri_component(input.to_string().as_str());
         format!(
-            "https://studio.apollographql.com/graph/{graph_id}/variant/{variant}/explorer?explorerURLState={encoded}",
+            "https://studio.apollographql.com/graph/{graph_id}/variant/{variant}/explorer?explorerURLState={compressed}",
             graph_id = self.graph_id,
             variant = self.variant
         )
     }
 
     pub async fn execute(&self, input: Value) -> Result<CallToolResult, McpError> {
-        webbrowser::open(self.create_explorer_url(&input).as_str())
+        // Validate field order: must be ["document", "variables", "headers"]
+        if let Value::Object(map) = &input {
+            let mut keys = map.keys();
+            if !(keys.next() == Some(&"document".to_string())
+                && keys.next() == Some(&"variables".to_string())
+                && keys.next() == Some(&"headers".to_string())
+                && keys.next().is_none())
+            {
+                return Err(McpError::new(
+                    ErrorCode::INVALID_PARAMS,
+                    "Input fields must be in order: document, variables, headers",
+                    None,
+                ));
+            }
+        } else {
+            return Err(McpError::new(
+                ErrorCode::INVALID_PARAMS,
+                "Input must be a JSON object",
+                None,
+            ));
+        }
+
+        let document = input.get("document").and_then(|v| v.as_str());
+        let variables = input.get("variables").and_then(|v| v.as_str());
+        let headers = input.get("headers").and_then(|v| v.as_str());
+
+        if document.is_none() || document == Some("") {
+            return Err(McpError::new(
+                ErrorCode::INVALID_PARAMS,
+                "Missing or empty 'document' field in input",
+                None,
+            ));
+        }
+        if variables.is_none() || variables == Some("") {
+            return Err(McpError::new(
+                ErrorCode::INVALID_PARAMS,
+                "Missing or empty 'variables' field in input",
+                None,
+            ));
+        }
+        if headers.is_none() || headers == Some("") {
+            return Err(McpError::new(
+                ErrorCode::INVALID_PARAMS,
+                "Missing or empty 'headers' field in input",
+                None,
+            ));
+        }
+
+        let url = self.create_explorer_url(&input);
+        info!(
+            "Opening Apollo Explorer URL: {} for input operation: {}",
+            url,
+            serde_json::to_string_pretty(&input).unwrap_or("<unable to serialize>".into())
+        );
+        webbrowser::open(url.as_str())
             .map(|_| CallToolResult {
                 content: vec![Content::text("success")],
                 is_error: None,
@@ -65,21 +118,22 @@ impl Explorer {
 #[cfg(test)]
 mod tests {
     use super::*;
+    use insta::assert_snapshot;
     use rmcp::serde_json::json;
 
     #[test]
     fn test_create_explorer_url() {
         let explorer = Explorer::new(String::from("mcp-example@mcp"));
         let input = json!({
             "document": "query GetWeatherAlerts($state: String!) {\n  alerts(state: $state) {\n    severity\n    description\n    instruction\n  }\n}",
-            "headers": "{}",
-            "variables": "{\"state\": \"CA\"}"
+            "variables": "{\"state\": \"CA\"}",
+            "headers": "{}"
         });
 
         let url = explorer.create_explorer_url(&input);
-        assert_eq!(
+        assert_snapshot!(
             url,
-            "https://studio.apollographql.com/graph/mcp-example/variant/mcp/explorer?explorerURLState=N4IgJg9gxgrgtgUwHYBcQC4QEcYIE4CeABAOIIoDqCAhigBb4CCANvigM4AUAJOyrQnREAyijwBLJAHMAhAEoiwADpIiRaqzwdOfAUN78UCBctVqi7BADd84lARXmiYBOygSADinEQkj85J8eDBQ3r7+AL4qESAANCAM1C547BggwDHxVtQS1ABGrKmYyiC6RkoYRBUAwowVMRFAAAA="
+            @"https://studio.apollographql.com/graph/mcp-example/variant/mcp/explorer?explorerURLState=N4IgJg9gxgrgtgUwHYBcQC4QEcYIE4CeABAOIIoDqCAhigBb4CCANvigM4AUAJOyrQnREAyijwBLJAHMAhAEoiwADpIiRaqzwdOfAUN78UCBctVqi7BADd84lARXmiYBOygSADinEQkj85J8eDBQ3r7+AL4qESAANCAM1C547BggwDHxVtQS1ABGrKmYyiC6RkoYRBUAwowVMRFAA"
         );
     }
 }