diff --git a/apps/admin-api/src/service.rs b/apps/admin-api/src/service.rs
index 440c00d..8bba890 100644
--- a/apps/admin-api/src/service.rs
+++ b/apps/admin-api/src/service.rs
@@ -3230,12 +3230,16 @@ fn build_request_preview(
     mapping: &MappingSet,
     input: &Value,
 ) -> Result<Value, crank_mapping::MappingError> {
-    let mapped = mapping.apply(&json!({ "mcp": input }))?;
-    let prepared = PreparedRequest::from_mapping_output(&mapped).map_err(|error| {
-        crank_mapping::MappingError::InvalidJsonPath {
-            path: error.to_string(),
-        }
-    })?;
+    let prepared = if mapping.is_empty() {
+        PreparedRequest::default()
+    } else {
+        let mapped = mapping.apply(&json!({ "mcp": input }))?;
+        PreparedRequest::from_mapping_output(&mapped).map_err(|error| {
+            crank_mapping::MappingError::InvalidJsonPath {
+                path: error.to_string(),
+            }
+        })?
+    };
 
     Ok(json!({
         "path": prepared.path_params,
diff --git a/crates/crank-runtime/src/executor.rs b/crates/crank-runtime/src/executor.rs
index dd19992..4400eda 100644
--- a/crates/crank-runtime/src/executor.rs
+++ b/crates/crank-runtime/src/executor.rs
@@ -123,6 +123,10 @@ impl RuntimeExecutor {
     ) -> Result<PreparedRequest, RuntimeError> {
         operation.input_schema.validate_shape(input)?;
 
+        if operation.input_mapping.is_empty() {
+            return Ok(PreparedRequest::default());
+        }
+
         let mapped_input = operation.input_mapping.apply(&json!({ "mcp": input }))?;
         PreparedRequest::from_mapping_output(&mapped_input)
     }
diff --git a/crates/crank-runtime/tests/integration.rs b/crates/crank-runtime/tests/integration.rs
new file mode 100644
index 0000000..9270287
--- /dev/null
+++ b/crates/crank-runtime/tests/integration.rs
@@ -0,0 +1,3 @@
+mod integration {
+    mod no_input_get;
+}
diff --git a/crates/crank-runtime/tests/integration/no_input_get.rs b/crates/crank-runtime/tests/integration/no_input_get.rs
new file mode 100644
index 0000000..ac29679
--- /dev/null
+++ b/crates/crank-runtime/tests/integration/no_input_get.rs
@@ -0,0 +1,89 @@
+use std::collections::BTreeMap;
+
+use crank_core::{
+    ExecutionConfig, HttpMethod, Operation, OperationId, OperationSecurityLevel, OperationStatus,
+    Protocol, RestTarget, Target, ToolDescription,
+};
+use crank_mapping::MappingSet;
+use crank_runtime::RuntimeExecutor;
+use crank_schema::{Schema, SchemaKind};
+use serde_json::json;
+use time::OffsetDateTime;
+
+#[test]
+fn prepares_empty_request_for_no_input_get_with_empty_mapping() {
+    let executor = RuntimeExecutor::new();
+    let operation = no_input_get_operation();
+
+    let request = executor
+        .prepare_request(&operation.into(), &json!({}))
+        .unwrap();
+
+    assert!(request.path_params.is_empty());
+    assert!(request.query_params.is_empty());
+    assert!(request.headers.is_empty());
+    assert!(request.body.is_none());
+}
+
+fn no_input_get_operation() -> Operation<Schema, MappingSet> {
+    Operation {
+        id: OperationId::new("op_no_input_get"),
+        name: "internal_health".to_owned(),
+        display_name: "Internal Health".to_owned(),
+        category: "smoke".to_owned(),
+        protocol: Protocol::Rest,
+        security_level: OperationSecurityLevel::Standard,
+        status: OperationStatus::Draft,
+        version: 1,
+        target: Target::Rest(RestTarget {
+            base_url: "http://admin-api:3001".to_owned(),
+            method: HttpMethod::Get,
+            path_template: "/health".to_owned(),
+            static_headers: BTreeMap::new(),
+        }),
+        input_schema: Schema {
+            kind: SchemaKind::Object,
+            description: None,
+            required: true,
+            nullable: false,
+            default_value: None,
+            fields: BTreeMap::new(),
+            items: None,
+            enum_values: Vec::new(),
+            variants: Vec::new(),
+        },
+        output_schema: Schema {
+            kind: SchemaKind::Object,
+            description: None,
+            required: true,
+            nullable: false,
+            default_value: None,
+            fields: BTreeMap::new(),
+            items: None,
+            enum_values: Vec::new(),
+            variants: Vec::new(),
+        },
+        input_mapping: MappingSet { rules: Vec::new() },
+        output_mapping: MappingSet { rules: Vec::new() },
+        execution_config: ExecutionConfig {
+            timeout_ms: 1_000,
+            retry_policy: None,
+            response_cache: None,
+            auth_profile_ref: None,
+            headers: BTreeMap::new(),
+        },
+        tool_description: ToolDescription {
+            title: "Internal Health".to_owned(),
+            description: "Checks internal health.".to_owned(),
+            tags: Vec::new(),
+            examples: Vec::new(),
+        },
+        samples: None,
+        generated_draft: None,
+        config_export: None,
+        wizard_state: None,
+        created_at: OffsetDateTime::UNIX_EPOCH,
+        updated_at: OffsetDateTime::UNIX_EPOCH,
+        published_at: None,
+    }
+}