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fix(mcp): paginate tools/resources/prompts discovery via nextCursor (#1250, #1256)

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MCP servers are allowed by spec to paginate list responses. The old
implementation made a single request and stopped, silently dropping
subsequent pages. Servers that paginate at fewer items than their
total tool count (e.g. gbrain at 5 per page) would appear to expose
only those first few tools.

All four discovery methods now follow nextCursor until the server
signals no more pages, accumulating results across all pages:
  - discover_tools
  - discover_resources
  - discover_resource_templates
  - discover_prompts

Thanks to Liu-Vince for the original diagnosis and fix (PR #1256).
This commit is contained in:
Hunter Bown
2026-05-09 00:11:51 -05:00
parent 408708f13e
commit 808e981f56
1 changed files with 120 additions and 54 deletions
Download Patch File Download Diff File Expand all files Collapse all files
crates/tui/src/mcp.rs
+120 -54
View File
@@ -774,94 +774,160 @@ impl McpConnection {
/// Discover available tools from the MCP server
async fn discover_tools(&mut self) -> Result<()> {
let list_id = self.next_id();
self.send(serde_json::json!({
"jsonrpc": "2.0",
"id": list_id,
"method": "tools/list",
"params": {}
}))
.await?;
let mut cursor: Option<String> = None;
loop {
let list_id = self.next_id();
let params = match &cursor {
Some(c) => serde_json::json!({ "cursor": c }),
None => serde_json::json!({}),
};
self.send(serde_json::json!({
"jsonrpc": "2.0",
"id": list_id,
"method": "tools/list",
"params": params
}))
.await?;
let response = self.recv(list_id).await?;
let response = self.recv(list_id).await?;
let Some(result) = response.get("result") else {
break;
};
if let Some(result) = response.get("result")
&& let Some(tools) = result.get("tools")
{
self.tools = serde_json::from_value(tools.clone()).unwrap_or_default();
if let Some(tools) = result.get("tools") {
let page: Vec<McpTool> = serde_json::from_value(tools.clone()).unwrap_or_default();
self.tools.extend(page);
}
cursor = result
.get("nextCursor")
.and_then(|v| v.as_str())
.map(str::to_owned);
if cursor.is_none() {
break;
}
}
Ok(())
}
/// Discover available resources from the MCP server
async fn discover_resources(&mut self) -> Result<()> {
let list_id = self.next_id();
self.send(serde_json::json!({
"jsonrpc": "2.0",
"id": list_id,
"method": "resources/list",
"params": {}
}))
.await?;
let mut cursor: Option<String> = None;
loop {
let list_id = self.next_id();
let params = match &cursor {
Some(c) => serde_json::json!({ "cursor": c }),
None => serde_json::json!({}),
};
self.send(serde_json::json!({
"jsonrpc": "2.0",
"id": list_id,
"method": "resources/list",
"params": params
}))
.await?;
let response = self.recv(list_id).await?;
let response = self.recv(list_id).await?;
let Some(result) = response.get("result") else {
break;
};
if let Some(result) = response.get("result")
&& let Some(resources) = result.get("resources")
{
self.resources = serde_json::from_value(resources.clone()).unwrap_or_default();
if let Some(resources) = result.get("resources") {
let page: Vec<McpResource> =
serde_json::from_value(resources.clone()).unwrap_or_default();
self.resources.extend(page);
}
cursor = result
.get("nextCursor")
.and_then(|v| v.as_str())
.map(str::to_owned);
if cursor.is_none() {
break;
}
}
Ok(())
}
/// Discover available resource templates from the MCP server
async fn discover_resource_templates(&mut self) -> Result<()> {
let list_id = self.next_id();
self.send(serde_json::json!({
"jsonrpc": "2.0",
"id": list_id,
"method": "resources/templates/list",
"params": {}
}))
.await?;
let mut cursor: Option<String> = None;
loop {
let list_id = self.next_id();
let params = match &cursor {
Some(c) => serde_json::json!({ "cursor": c }),
None => serde_json::json!({}),
};
self.send(serde_json::json!({
"jsonrpc": "2.0",
"id": list_id,
"method": "resources/templates/list",
"params": params
}))
.await?;
let response = self.recv(list_id).await?;
let response = self.recv(list_id).await?;
let Some(result) = response.get("result") else {
break;
};
if let Some(result) = response.get("result") {
let templates = result
.get("resourceTemplates")
.or_else(|| result.get("templates"))
.or_else(|| result.get("resource_templates"));
if let Some(templates) = templates {
self.resource_templates =
let page: Vec<McpResourceTemplate> =
serde_json::from_value(templates.clone()).unwrap_or_default();
self.resource_templates.extend(page);
}
cursor = result
.get("nextCursor")
.and_then(|v| v.as_str())
.map(str::to_owned);
if cursor.is_none() {
break;
}
}
Ok(())
}
/// Discover available prompts from the MCP server
async fn discover_prompts(&mut self) -> Result<()> {
let list_id = self.next_id();
self.send(serde_json::json!({
"jsonrpc": "2.0",
"id": list_id,
"method": "prompts/list",
"params": {}
}))
.await?;
let mut cursor: Option<String> = None;
loop {
let list_id = self.next_id();
let params = match &cursor {
Some(c) => serde_json::json!({ "cursor": c }),
None => serde_json::json!({}),
};
self.send(serde_json::json!({
"jsonrpc": "2.0",
"id": list_id,
"method": "prompts/list",
"params": params
}))
.await?;
let response = self.recv(list_id).await?;
let response = self.recv(list_id).await?;
let Some(result) = response.get("result") else {
break;
};
if let Some(result) = response.get("result")
&& let Some(prompts) = result.get("prompts")
{
self.prompts = serde_json::from_value(prompts.clone()).unwrap_or_default();
if let Some(prompts) = result.get("prompts") {
let page: Vec<McpPrompt> =
serde_json::from_value(prompts.clone()).unwrap_or_default();
self.prompts.extend(page);
}
cursor = result
.get("nextCursor")
.and_then(|v| v.as_str())
.map(str::to_owned);
if cursor.is_none() {
break;
}
}
Ok(())
}