diff --git a/zlink-core/Cargo.toml b/zlink-core/Cargo.toml
index e55c03f8..76e3b961 100644
--- a/zlink-core/Cargo.toml
+++ b/zlink-core/Cargo.toml
@@ -13,11 +13,11 @@ default = ["std", "server", "proxy", "tracing"]
 std = ["dep:rustix", "dep:libc", "zlink-macros/std"]
 server = []
 proxy = ["zlink-macros/proxy"]
-service = ["server", "zlink-macros/service", "introspection"]
+service = ["server", "zlink-macros/service"]
 # IDL and introspection support
 idl = []
 idl-parse = ["idl", "dep:winnow", "zlink-macros/idl-parse"]
-introspection = ["std", "idl", "zlink-macros/introspection"]
+introspection = ["idl", "zlink-macros/introspection"]
 
 [dependencies]
 serde = { version = "1.0.218", default-features = false, features = ["derive", "alloc"] }
diff --git a/zlink-core/src/introspect/type/collections.rs b/zlink-core/src/introspect/type/collections.rs
index 58073c5a..ed9f79e4 100644
--- a/zlink-core/src/introspect/type/collections.rs
+++ b/zlink-core/src/introspect/type/collections.rs
@@ -1,8 +1,14 @@
 //! Type implementations for collection types.
 
+use alloc::{
+    collections::{BTreeMap, BTreeSet},
+    string::String,
+    vec::Vec,
+};
+
 use super::Type;
 use crate::{idl, idl::TypeRef};
-use alloc::collections::{BTreeMap, BTreeSet};
+#[cfg(feature = "std")]
 use std::collections::{HashMap, HashSet};
 
 // ============================================================================
@@ -23,10 +29,12 @@ impl<T: Type> Type for &[T] {
 // Map types - Varlink maps always have string keys
 // ============================================================================
 
+#[cfg(feature = "std")]
 impl<V: Type> Type for HashMap<String, V> {
     const TYPE: &'static idl::Type<'static> = &idl::Type::Map(TypeRef::new(V::TYPE));
 }
 
+#[cfg(feature = "std")]
 impl<V: Type> Type for HashMap<&str, V> {
     const TYPE: &'static idl::Type<'static> = &idl::Type::Map(TypeRef::new(V::TYPE));
 }
@@ -43,6 +51,7 @@ impl<V: Type> Type for BTreeMap<&str, V> {
 // Set types - represented as arrays in Varlink
 // ============================================================================
 
+#[cfg(feature = "std")]
 impl<T: Type> Type for HashSet<T> {
     const TYPE: &'static idl::Type<'static> = &idl::Type::Array(TypeRef::new(T::TYPE));
 }
diff --git a/zlink-core/src/introspect/type/primitives.rs b/zlink-core/src/introspect/type/primitives.rs
index efa3a8af..b667c26b 100644
--- a/zlink-core/src/introspect/type/primitives.rs
+++ b/zlink-core/src/introspect/type/primitives.rs
@@ -1,5 +1,7 @@
 //! Type implementations for primitive types.
 
+use alloc::string::String;
+
 use super::Type;
 use crate::idl;
 
diff --git a/zlink-core/src/introspect/type/special.rs b/zlink-core/src/introspect/type/special.rs
index 407f93f8..9add8132 100644
--- a/zlink-core/src/introspect/type/special.rs
+++ b/zlink-core/src/introspect/type/special.rs
@@ -33,10 +33,12 @@ impl Type for core::time::Duration {
     const TYPE: &'static idl::Type<'static> = &idl::Type::Float;
 }
 
+#[cfg(feature = "std")]
 impl Type for std::time::Instant {
     const TYPE: &'static idl::Type<'static> = &idl::Type::Float;
 }
 
+#[cfg(feature = "std")]
 impl Type for std::time::SystemTime {
     const TYPE: &'static idl::Type<'static> = &idl::Type::Float;
 }
@@ -45,10 +47,12 @@ impl Type for std::time::SystemTime {
 // Path types
 // ============================================================================
 
+#[cfg(feature = "std")]
 impl Type for std::path::PathBuf {
     const TYPE: &'static idl::Type<'static> = &idl::Type::String;
 }
 
+#[cfg(feature = "std")]
 impl Type for std::path::Path {
     const TYPE: &'static idl::Type<'static> = &idl::Type::String;
 }
@@ -57,10 +61,12 @@ impl Type for std::path::Path {
 // OS string types
 // ============================================================================
 
+#[cfg(feature = "std")]
 impl Type for std::ffi::OsString {
     const TYPE: &'static idl::Type<'static> = &idl::Type::String;
 }
 
+#[cfg(feature = "std")]
 impl Type for std::ffi::OsStr {
     const TYPE: &'static idl::Type<'static> = &idl::Type::String;
 }
diff --git a/zlink-core/src/introspect/type/wrappers.rs b/zlink-core/src/introspect/type/wrappers.rs
index 0aa483b1..d8c1cd43 100644
--- a/zlink-core/src/introspect/type/wrappers.rs
+++ b/zlink-core/src/introspect/type/wrappers.rs
@@ -3,6 +3,13 @@
 //! This module contains implementations for types that transparently wrap other types,
 //! such as smart pointers, cells, and optional types.
 
+use alloc::{
+    borrow::{Cow, ToOwned},
+    boxed::Box,
+    rc::Rc,
+    sync::Arc,
+};
+
 use super::Type;
 use crate::{idl, idl::TypeRef};
 
@@ -22,11 +29,11 @@ impl<T: Type + ?Sized> Type for Box<T> {
     const TYPE: &'static idl::Type<'static> = T::TYPE;
 }
 
-impl<T: Type + ?Sized> Type for std::rc::Rc<T> {
+impl<T: Type + ?Sized> Type for Rc<T> {
     const TYPE: &'static idl::Type<'static> = T::TYPE;
 }
 
-impl<T: Type + ?Sized> Type for std::sync::Arc<T> {
+impl<T: Type + ?Sized> Type for Arc<T> {
     const TYPE: &'static idl::Type<'static> = T::TYPE;
 }
 
@@ -46,6 +53,6 @@ impl<T: Type + ?Sized> Type for core::cell::RefCell<T> {
 // Cow type - transparent wrapper
 // ============================================================================
 
-impl<T: Type + ToOwned + ?Sized> Type for std::borrow::Cow<'_, T> {
+impl<T: Type + ToOwned + ?Sized> Type for Cow<'_, T> {
     const TYPE: &'static idl::Type<'static> = T::TYPE;
 }
diff --git a/zlink-macros/src/service/method.rs b/zlink-macros/src/service/method.rs
index 4193d4ba..2b7c3f87 100644
--- a/zlink-macros/src/service/method.rs
+++ b/zlink-macros/src/service/method.rs
@@ -112,6 +112,14 @@ impl MethodInfo {
                 "at most one `#[zlink(fds)]` parameter is allowed per method",
             ));
         }
+        #[cfg(not(feature = "std"))]
+        if !fds_params.is_empty() || return_fds {
+            return Err(Error::new_spanned(
+                &method.sig,
+                "FD-related attributes (`#[zlink(fds)]` and `#[zlink(return_fds)]`) \
+                 require the `std` feature to be enabled",
+            ));
+        }
 
         // Extract return type and check if it's a Result or Stream.
         let (
diff --git a/zlink-smol/Cargo.toml b/zlink-smol/Cargo.toml
index 5f9c69bf..e09cd00c 100644
--- a/zlink-smol/Cargo.toml
+++ b/zlink-smol/Cargo.toml
@@ -12,7 +12,7 @@ authors.workspace = true
 default = ["service", "proxy", "tracing"]
 server = ["zlink-core/server"]
 proxy = ["zlink-core/proxy"]
-service = ["server", "introspection", "zlink-core/service"]
+service = ["server", "zlink-core/service"]
 idl = ["zlink-core/idl"]
 idl-parse = ["zlink-core/idl-parse"]
 introspection = ["zlink-core/introspection"]
diff --git a/zlink-tokio/Cargo.toml b/zlink-tokio/Cargo.toml
index 83122033..e9c3901d 100644
--- a/zlink-tokio/Cargo.toml
+++ b/zlink-tokio/Cargo.toml
@@ -12,7 +12,7 @@ authors.workspace = true
 default = ["service", "proxy", "tracing"]
 server = ["zlink-core/server"]
 proxy = ["zlink-core/proxy"]
-service = ["server", "introspection", "zlink-core/service"]
+service = ["server", "zlink-core/service"]
 idl = ["zlink-core/idl"]
 idl-parse = ["zlink-core/idl-parse"]
 introspection = ["zlink-core/introspection"]