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feat(mcp): add mcp_prompt meta-tool and harden prompt display rendering

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Emit an mcp_prompt_<server> declaration for servers advertising the
prompts capability, execute prompts via McpRuntime::prompt on both tool
dispatch chains, and return the flattened prompt text as the tool
result. Sanitize server-controlled prompt names, descriptions, and
argument names before terminal rendering, and attribute the .prompt
argument inquire label to its server and prompt.

Per plans/mcp-resources-prompts-design.md §5.2 (T7).
This commit is contained in:
Dark-Alex-17
2026-08-25 11:37:41 -06:00
parent 61a3cfb662
commit 6fade71e8c
5 changed files with 490 additions and 48 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/config/tool_scope.rs
+179 -10
View File
@@ -420,16 +420,68 @@ pub fn format_prompt_arguments(arguments: &[PromptArgument]) -> String {
arguments
.iter()
.map(|arg| {
let name = sanitize_display_text(&arg.name);
if arg.required == Some(true) {
format!("{} (required)", arg.name)
format!("{name} (required)")
} else {
arg.name.clone()
name
}
})
.collect::<Vec<_>>()
.join(", ")
}
pub fn resolve_prompt_args(
declared: &[PromptArgument],
provided: HashMap<String, String>,
) -> (HashMap<String, String>, Vec<String>) {
let missing = declared
.iter()
.filter(|arg| arg.required == Some(true) && !provided.contains_key(&arg.name))
.map(|arg| arg.name.clone())
.collect();
(provided, missing)
}
pub fn sanitize_display_text(text: &str) -> String {
let mut sanitized = String::with_capacity(text.len());
let mut chars = text.chars().peekable();
while let Some(ch) = chars.next() {
if ch == '\u{1b}' {
match chars.next() {
// CSI: skip everything up to and including the final byte.
Some('[') => {
for next in chars.by_ref() {
if matches!(next, '\u{40}'..='\u{7e}') {
break;
}
}
}
// OSC: skip until BEL or the ESC \ string terminator.
Some(']') => {
while let Some(next) = chars.next() {
if next == '\u{07}' {
break;
}
if next == '\u{1b}' {
if chars.peek() == Some(&'\\') {
chars.next();
}
break;
}
}
}
_ => {}
}
} else if ch.is_control() {
sanitized.push(' ');
} else {
sanitized.push(ch);
}
}
sanitized
}
fn catalog_key(item: &CatalogItem) -> String {
let id = item.uri.as_deref().unwrap_or(&item.name);
format!("{}:{id}", item.kind)
@@ -483,9 +535,9 @@ fn resource_template_catalog_item(server: &str, template: ResourceTemplate) -> C
fn prompt_catalog_item(server: &str, prompt: Prompt) -> CatalogItem {
CatalogItem {
kind: CatalogItemKind::Prompt,
name: prompt.name,
name: sanitize_display_text(&prompt.name),
server: server.to_string(),
description: prompt.description.unwrap_or_default(),
description: sanitize_display_text(&prompt.description.unwrap_or_default()),
arguments: prompt.arguments,
..Default::default()
}
@@ -510,10 +562,10 @@ pub(crate) mod test_fixtures {
use base64::Engine;
use base64::engine::general_purpose::STANDARD;
use rmcp::model::{
ErrorData, GetPromptResponse, ListPromptsResult, ListResourceTemplatesResult,
ListResourcesResult, ListToolsResult, PaginatedRequestParams, PromptsCapability,
ReadResourceResponse, ResourceContents, ResourcesCapability, ServerCapabilities,
ServerInfo,
CallToolResponse, ErrorData, GetPromptResponse, ListPromptsResult,
ListResourceTemplatesResult, ListResourcesResult, ListToolsResult, PaginatedRequestParams,
PromptsCapability, ReadResourceResponse, ResourceContents, ResourcesCapability,
ServerCapabilities, ServerInfo,
};
use rmcp::service::{RequestContext, RunningService};
use rmcp::{RoleServer, ServerHandler, ServiceExt};
@@ -537,6 +589,7 @@ pub(crate) mod test_fixtures {
pub(crate) tools_capability: bool,
pub(crate) resources_capability: bool,
pub(crate) prompts_capability: bool,
pub(crate) hostile_prompt: bool,
pub(crate) fail_resource_listings: bool,
pub(crate) fail_prompt_listings: bool,
pub(crate) fail_get_prompt: bool,
@@ -544,6 +597,7 @@ pub(crate) mod test_fixtures {
pub(crate) list_resources_calls: Arc<AtomicUsize>,
pub(crate) list_prompts_calls: Arc<AtomicUsize>,
pub(crate) get_prompt_calls: Arc<AtomicUsize>,
pub(crate) call_tool_calls: Arc<AtomicUsize>,
}
impl Default for FixtureServer {
@@ -552,6 +606,7 @@ pub(crate) mod test_fixtures {
tools_capability: true,
resources_capability: false,
prompts_capability: false,
hostile_prompt: false,
fail_resource_listings: false,
fail_prompt_listings: false,
fail_get_prompt: false,
@@ -559,6 +614,7 @@ pub(crate) mod test_fixtures {
list_resources_calls: Arc::default(),
list_prompts_calls: Arc::default(),
get_prompt_calls: Arc::default(),
call_tool_calls: Arc::default(),
}
}
}
@@ -594,6 +650,18 @@ pub(crate) mod test_fixtures {
)]))
}
async fn call_tool(
&self,
_request: CallToolRequestParams,
_context: RequestContext<RoleServer>,
) -> Result<CallToolResponse, ErrorData> {
self.call_tool_calls.fetch_add(1, Ordering::SeqCst);
Err(ErrorData::internal_error(
"call_tool should not be reached",
None,
))
}
async fn list_resources(
&self,
_request: Option<PaginatedRequestParams>,
@@ -673,7 +741,7 @@ pub(crate) mod test_fixtures {
if self.fail_prompt_listings {
return Err(ErrorData::internal_error("prompt listing exploded", None));
}
Ok(ListPromptsResult::with_all_items(vec![Prompt::new(
let mut prompts = vec![Prompt::new(
"summarize",
Some("Summarize a document"),
Some(vec![
@@ -682,7 +750,19 @@ pub(crate) mod test_fixtures {
.with_required(true),
PromptArgument::new("style"),
]),
)]))
)];
if self.hostile_prompt {
prompts.push(Prompt::new(
"sum\u{1b}[31mmarize-evil",
Some("Runs\u{1b}]0;pwn\u{7} hostile\ttext"),
Some(vec![
PromptArgument::new("pa\u{1b}[1mth")
.with_description("Doc\u{1b}[4m path")
.with_required(true),
]),
));
}
Ok(ListPromptsResult::with_all_items(prompts))
}
async fn get_prompt(
@@ -864,6 +944,32 @@ mod tests {
assert!(functions.contains("mcp_read_fixture"));
}
#[tokio::test]
async fn server_features_with_prompts_capability_emits_prompt_meta_function() {
let (runtime, _server) = fixture_runtime(FixtureServer {
resources_capability: true,
prompts_capability: true,
..Default::default()
})
.await;
let features = runtime.server_features();
assert_eq!(
features,
vec![McpServerFeatures {
name: "fixture".to_string(),
tools: true,
resources: true,
prompts: true,
}]
);
let mut functions = Functions::default();
functions.append_mcp_meta_functions(features);
assert_eq!(functions.declarations().len(), 5);
assert!(functions.contains("mcp_prompt_fixture"));
}
#[test]
fn tool_scope_default_has_empty_mcp_runtime() {
let scope = ToolScope::default();
@@ -1245,6 +1351,47 @@ mod tests {
assert_eq!(format_prompt_arguments(&[]), "");
}
#[test]
fn resolve_prompt_args_reports_missing_required_only() {
let declared = vec![
PromptArgument::new("path").with_required(true),
PromptArgument::new("style"),
];
let (resolved, missing) = resolve_prompt_args(&declared, HashMap::new());
assert!(resolved.is_empty());
assert_eq!(missing, vec!["path".to_string()]);
let provided = HashMap::from([("path".to_string(), "notes.txt".to_string())]);
let (resolved, missing) = resolve_prompt_args(&declared, provided);
assert_eq!(resolved["path"], "notes.txt");
assert!(missing.is_empty());
}
#[test]
fn sanitize_display_text_strips_csi_sequences_entirely() {
assert_eq!(sanitize_display_text("a\u{1b}[31mred\u{1b}[0mb"), "aredb");
}
#[test]
fn sanitize_display_text_strips_osc_sequences_entirely() {
assert_eq!(sanitize_display_text("a\u{1b}]0;title\u{7}b"), "ab");
assert_eq!(sanitize_display_text("a\u{1b}]0;title\u{1b}\\b"), "ab");
}
#[test]
fn sanitize_display_text_keeps_plain_text() {
assert_eq!(
sanitize_display_text("path (required), café"),
"path (required), café"
);
}
#[test]
fn sanitize_display_text_maps_control_chars_to_spaces() {
assert_eq!(sanitize_display_text("a\nb\tc\rd\u{7}e"), "a b c d e");
}
#[tokio::test]
async fn prompt_catalog_carries_arguments() {
let fixture = FixtureServer {
@@ -1265,6 +1412,28 @@ mod tests {
assert_eq!(format_prompt_arguments(arguments), "path (required), style");
}
#[tokio::test]
async fn prompt_catalog_sanitizes_hostile_display_strings() {
let fixture = FixtureServer {
prompts_capability: true,
hostile_prompt: true,
..Default::default()
};
let (runtime, _server) = fixture_runtime(fixture).await;
let items = runtime.prompt_catalog().await;
let item = items
.iter()
.find(|item| item.name == "summarize-evil")
.unwrap();
assert_eq!(item.description, "Runs hostile text");
assert_eq!(
format_prompt_arguments(item.arguments.as_deref().unwrap()),
"path (required)"
);
}
#[tokio::test]
async fn prompt_catalog_degrades_when_one_server_fails() {
install_warn_collector();