fix(schema): Reject malformed protocol fields

agent-client-protocol-schema/src/v1/agent.rs

@@ -1740,13 +1740,9 @@ impl CloseSessionResponse {
 #[non_exhaustive]
 pub struct ListSessionsRequest {
     /// Filter sessions by working directory. Must be an absolute path.
-    #[serde_as(deserialize_as = "DefaultOnError")]
-    #[schemars(extend("x-deserialize-default-on-error" = true))]
     #[serde(default)]
     pub cwd: Option<PathBuf>,
     /// Opaque cursor token from a previous response's nextCursor field for cursor-based pagination
-    #[serde_as(deserialize_as = "DefaultOnError")]
-    #[schemars(extend("x-deserialize-default-on-error" = true))]
     #[serde(default)]
     pub cursor: Option<String>,
     /// The _meta property is reserved by ACP to allow clients and agents to attach additional
@@ -2899,8 +2895,6 @@ pub struct McpServerHttp {
     /// URL to the MCP server.
     pub url: String,
     /// HTTP headers to set when making requests to the MCP server.
-    #[serde_as(deserialize_as = "DefaultOnError<VecSkipError<_, SkipListener>>")]
-    #[schemars(extend("x-deserialize-default-on-error" = true, "x-deserialize-skip-invalid-items" = true))]
     pub headers: Vec<HttpHeader>,
     /// The _meta property is reserved by ACP to allow clients and agents to attach additional
     /// metadata to their interactions. Implementations MUST NOT make assumptions about values at
@@ -2957,8 +2951,6 @@ pub struct McpServerSse {
     /// URL to the MCP server.
     pub url: String,
     /// HTTP headers to set when making requests to the MCP server.
-    #[serde_as(deserialize_as = "DefaultOnError<VecSkipError<_, SkipListener>>")]
-    #[schemars(extend("x-deserialize-default-on-error" = true, "x-deserialize-skip-invalid-items" = true))]
     pub headers: Vec<HttpHeader>,
     /// The _meta property is reserved by ACP to allow clients and agents to attach additional
     /// metadata to their interactions. Implementations MUST NOT make assumptions about values at
@@ -3098,12 +3090,8 @@ pub struct McpServerStdio {
     /// Absolute path to the MCP server executable.
     pub command: PathBuf,
     /// Command-line arguments to pass to the MCP server.
-    #[serde_as(deserialize_as = "DefaultOnError<VecSkipError<_, SkipListener>>")]
-    #[schemars(extend("x-deserialize-default-on-error" = true, "x-deserialize-skip-invalid-items" = true))]
     pub args: Vec<String>,
     /// Environment variables to set when launching the MCP server.
-    #[serde_as(deserialize_as = "DefaultOnError<VecSkipError<_, SkipListener>>")]
-    #[schemars(extend("x-deserialize-default-on-error" = true, "x-deserialize-skip-invalid-items" = true))]
     pub env: Vec<EnvVariable>,
     /// The _meta property is reserved by ACP to allow clients and agents to attach additional
     /// metadata to their interactions. Implementations MUST NOT make assumptions about values at
@@ -3277,8 +3265,6 @@ pub struct PromptRequest {
     /// When available, [`ContentBlock::Resource`] is preferred
     /// as it avoids extra round-trips and allows the message to include
     /// pieces of context from sources the agent may not have access to.
-    #[serde_as(deserialize_as = "DefaultOnError<VecSkipError<_, SkipListener>>")]
-    #[schemars(extend("x-deserialize-default-on-error" = true, "x-deserialize-skip-invalid-items" = true))]
     pub prompt: Vec<ContentBlock>,
     /// The _meta property is reserved by ACP to allow clients and agents to attach additional
     /// metadata to their interactions. Implementations MUST NOT make assumptions about values at
@@ -3636,8 +3622,6 @@ pub struct ProviderInfo {
     pub required: bool,
     /// Current effective non-secret routing config.
     /// Null or omitted means provider is disabled.
-    #[serde_as(deserialize_as = "DefaultOnError")]
-    #[schemars(extend("x-deserialize-default-on-error" = true))]
     #[serde(default)]
     pub current: Option<ProviderCurrentConfig>,
     /// The _meta property is reserved by ACP to allow clients and agents to attach additional
@@ -3742,8 +3726,6 @@ impl ListProvidersRequest {
 #[non_exhaustive]
 pub struct ListProvidersResponse {
     /// Configurable providers with current routing info suitable for UI display.
-    #[serde_as(deserialize_as = "DefaultOnError<VecSkipError<_, SkipListener>>")]
-    #[schemars(extend("x-deserialize-default-on-error" = true, "x-deserialize-skip-invalid-items" = true))]
     pub providers: Vec<ProviderInfo>,
     /// The _meta property is reserved by ACP to allow clients and agents to attach additional
     /// metadata to their interactions. Implementations MUST NOT make assumptions about values at
@@ -3803,8 +3785,6 @@ pub struct SetProviderRequest {
     pub base_url: String,
     /// Full headers map for this provider.
     /// May include authorization, routing, or other integration-specific headers.
-    #[serde_as(deserialize_as = "DefaultOnError")]
-    #[schemars(extend("x-deserialize-default-on-error" = true))]
     #[serde(default, skip_serializing_if = "HashMap::is_empty")]
     pub headers: HashMap<String, String>,
     /// The _meta property is reserved by ACP to allow clients and agents to attach additional
@@ -6661,4 +6641,30 @@ mod test_serialization {
         let deserialized: AgentCapabilities = serde_json::from_value(json).unwrap();
         assert!(deserialized.providers.is_some());
     }
+
+    #[test]
+    fn prompt_request_rejects_malformed_content_block() {
+        use serde_json::json;
+
+        assert!(
+            serde_json::from_value::<PromptRequest>(json!({
+                "sessionId": "sess-1",
+                "prompt": [{"type": "text"}]
+            }))
+            .is_err()
+        );
+    }
+
+    #[test]
+    fn prompt_request_rejects_non_array_prompt() {
+        use serde_json::json;
+
+        assert!(
+            serde_json::from_value::<PromptRequest>(json!({
+                "sessionId": "sess-1",
+                "prompt": "hello"
+            }))
+            .is_err()
+        );
+    }
 }

agent-client-protocol-schema/src/v1/client.rs

@@ -656,8 +656,6 @@ pub struct RequestPermissionRequest {
     /// Details about the tool call requiring permission.
     pub tool_call: ToolCallUpdate,
     /// Available permission options for the user to choose from.
-    #[serde_as(deserialize_as = "DefaultOnError<VecSkipError<_, SkipListener>>")]
-    #[schemars(extend("x-deserialize-default-on-error" = true, "x-deserialize-skip-invalid-items" = true))]
     pub options: Vec<PermissionOption>,
     /// The _meta property is reserved by ACP to allow clients and agents to attach additional
     /// metadata to their interactions. Implementations MUST NOT make assumptions about values at
@@ -2982,4 +2980,26 @@ mod tests {
         .unwrap();
         assert_eq!(request_with_null_params.params, None);
     }
+
+    #[test]
+    fn request_permission_request_rejects_malformed_options() {
+        use serde_json::json;
+
+        assert!(
+            serde_json::from_value::<RequestPermissionRequest>(json!({
+                "sessionId": "sess-1",
+                "toolCall": {"toolCallId": "tc-1"},
+                "options": "not-an-array"
+            }))
+            .is_err()
+        );
+        assert!(
+            serde_json::from_value::<RequestPermissionRequest>(json!({
+                "sessionId": "sess-1",
+                "toolCall": {"toolCallId": "tc-1"},
+                "options": [{"optionId": "allow"}]
+            }))
+            .is_err()
+        );
+    }
 }

agent-client-protocol-schema/src/v1/elicitation.rs

@@ -131,23 +131,15 @@ pub struct StringPropertySchema {
     #[serde(default)]
     pub description: Option<String>,
     /// Minimum string length.
-    #[serde_as(deserialize_as = "DefaultOnError")]
-    #[schemars(extend("x-deserialize-default-on-error" = true))]
     #[serde(default)]
     pub min_length: Option<u32>,
     /// Maximum string length.
-    #[serde_as(deserialize_as = "DefaultOnError")]
-    #[schemars(extend("x-deserialize-default-on-error" = true))]
     #[serde(default)]
     pub max_length: Option<u32>,
     /// Pattern the string must match.
-    #[serde_as(deserialize_as = "DefaultOnError")]
-    #[schemars(extend("x-deserialize-default-on-error" = true))]
     #[serde(default)]
     pub pattern: Option<String>,
     /// String format.
-    #[serde_as(deserialize_as = "DefaultOnError")]
-    #[schemars(extend("x-deserialize-default-on-error" = true))]
     #[serde(default)]
     pub format: Option<StringFormat>,
     /// Default value.
@@ -156,14 +148,10 @@ pub struct StringPropertySchema {
     #[serde(default)]
     pub default: Option<String>,
     /// Enum values for untitled single-select enums.
-    #[serde_as(deserialize_as = "DefaultOnError<Option<VecSkipError<_, SkipListener>>>")]
-    #[schemars(extend("x-deserialize-default-on-error" = true, "x-deserialize-skip-invalid-items" = true))]
     #[serde(default)]
     #[serde(rename = "enum")]
     pub enum_values: Option<Vec<String>>,
     /// Titled enum options for titled single-select enums.
-    #[serde_as(deserialize_as = "DefaultOnError<Option<VecSkipError<_, SkipListener>>>")]
-    #[schemars(extend("x-deserialize-default-on-error" = true, "x-deserialize-skip-invalid-items" = true))]
     #[serde(default)]
     #[serde(rename = "oneOf")]
     pub one_of: Option<Vec<EnumOption>>,
@@ -315,13 +303,9 @@ pub struct NumberPropertySchema {
     #[serde(default)]
     pub description: Option<String>,
     /// Minimum value (inclusive).
-    #[serde_as(deserialize_as = "DefaultOnError")]
-    #[schemars(extend("x-deserialize-default-on-error" = true))]
     #[serde(default)]
     pub minimum: Option<f64>,
     /// Maximum value (inclusive).
-    #[serde_as(deserialize_as = "DefaultOnError")]
-    #[schemars(extend("x-deserialize-default-on-error" = true))]
     #[serde(default)]
     pub maximum: Option<f64>,
     /// Default value.
@@ -413,13 +397,9 @@ pub struct IntegerPropertySchema {
     #[serde(default)]
     pub description: Option<String>,
     /// Minimum value (inclusive).
-    #[serde_as(deserialize_as = "DefaultOnError")]
-    #[schemars(extend("x-deserialize-default-on-error" = true))]
     #[serde(default)]
     pub minimum: Option<i64>,
     /// Maximum value (inclusive).
-    #[serde_as(deserialize_as = "DefaultOnError")]
-    #[schemars(extend("x-deserialize-default-on-error" = true))]
     #[serde(default)]
     pub maximum: Option<i64>,
     /// Default value.
@@ -574,8 +554,6 @@ impl BooleanPropertySchema {
 #[non_exhaustive]
 pub struct StringMultiSelectItems {
     /// Allowed enum values.
-    #[serde_as(deserialize_as = "DefaultOnError<VecSkipError<_, SkipListener>>")]
-    #[schemars(extend("x-deserialize-default-on-error" = true, "x-deserialize-skip-invalid-items" = true))]
     #[serde(rename = "enum")]
     pub values: Vec<String>,
     /// The _meta property is reserved by ACP to allow clients and agents to attach additional
@@ -616,8 +594,6 @@ impl StringMultiSelectItems {
 #[non_exhaustive]
 pub struct TitledMultiSelectItems {
     /// Titled enum options.
-    #[serde_as(deserialize_as = "DefaultOnError<VecSkipError<_, SkipListener>>")]
-    #[schemars(extend("x-deserialize-default-on-error" = true, "x-deserialize-skip-invalid-items" = true))]
     #[serde(rename = "anyOf")]
     pub options: Vec<EnumOption>,
     /// The _meta property is reserved by ACP to allow clients and agents to attach additional
@@ -772,13 +748,9 @@ pub struct MultiSelectPropertySchema {
     #[serde(default)]
     pub description: Option<String>,
     /// Minimum number of items to select.
-    #[serde_as(deserialize_as = "DefaultOnError")]
-    #[schemars(extend("x-deserialize-default-on-error" = true))]
     #[serde(default)]
     pub min_items: Option<u64>,
     /// Maximum number of items to select.
-    #[serde_as(deserialize_as = "DefaultOnError")]
-    #[schemars(extend("x-deserialize-default-on-error" = true))]
     #[serde(default)]
     pub max_items: Option<u64>,
     /// The items definition describing allowed values.
@@ -1054,13 +1026,9 @@ pub struct ElicitationSchema {
     #[serde(default)]
     pub title: Option<String>,
     /// Property definitions (must be primitive types).
-    #[serde_as(deserialize_as = "DefaultOnError")]
-    #[schemars(extend("x-deserialize-default-on-error" = true))]
     #[serde(default)]
     pub properties: BTreeMap<String, ElicitationPropertySchema>,
     /// List of required property names.
-    #[serde_as(deserialize_as = "DefaultOnError<Option<VecSkipError<_, SkipListener>>>")]
-    #[schemars(extend("x-deserialize-default-on-error" = true, "x-deserialize-skip-invalid-items" = true))]
     #[serde(default)]
     pub required: Option<Vec<String>>,
     /// Optional description of what this schema represents.
@@ -1951,8 +1919,6 @@ impl From<OtherElicitationAction> for ElicitationAction {
 #[non_exhaustive]
 pub struct ElicitationAcceptAction {
     /// The user-provided content, if any, as an object matching the requested schema.
-    #[serde_as(deserialize_as = "DefaultOnError")]
-    #[schemars(extend("x-deserialize-default-on-error" = true))]
     #[serde(default)]
     pub content: Option<BTreeMap<String, ElicitationContentValue>>,
 }
@@ -2781,34 +2747,28 @@ mod tests {
     }
 
     #[test]
-    fn response_accept_defaults_non_object_content() {
-        let response = serde_json::from_value::<CreateElicitationResponse>(json!({
-            "action": "accept",
-            "content": "Alice"
-        }))
-        .unwrap();
-
-        assert_eq!(
-            response.action,
-            ElicitationAction::Accept(ElicitationAcceptAction::new())
+    fn response_accept_rejects_non_object_content() {
+        assert!(
+            serde_json::from_value::<CreateElicitationResponse>(json!({
+                "action": "accept",
+                "content": "Alice"
+            }))
+            .is_err()
         );
     }
 
     #[test]
-    fn response_accept_defaults_nested_object_content() {
-        let response = serde_json::from_value::<CreateElicitationResponse>(json!({
-            "action": "accept",
-            "content": {
-                "profile": {
-                    "name": "Alice"
+    fn response_accept_rejects_nested_object_content() {
+        assert!(
+            serde_json::from_value::<CreateElicitationResponse>(json!({
+                "action": "accept",
+                "content": {
+                    "profile": {
+                        "name": "Alice"
+                    }
                 }
-            }
-        }))
-        .unwrap();
-
-        assert_eq!(
-            response.action,
-            ElicitationAction::Accept(ElicitationAcceptAction::new())
+            }))
+            .is_err()
         );
     }
 

agent-client-protocol-schema/src/v1/mcp.rs

@@ -146,8 +146,6 @@ pub struct MessageMcpRequest {
     /// Optional inner MCP params.
     ///
     /// If omitted or set to `null`, the inner MCP message has no params.
-    #[serde_as(deserialize_as = "DefaultOnError")]
-    #[schemars(extend("x-deserialize-default-on-error" = true))]
     #[serde(default)]
     pub params: Option<serde_json::Map<String, serde_json::Value>>,
     /// The _meta property is reserved by ACP to allow clients and agents to attach additional