feat(mcp): include source section in list/describe source tools

.changeset/mcp-source-section.md

@@ -0,0 +1,10 @@
+---
+"@hyperdx/api": patch
+---
+
+feat: include the source Section in MCP source tools
+
+The `clickstack_list_sources` and `clickstack_describe_source` MCP tools now
+return the optional Section label on each source, so agents see the same source
+grouping that the source selector shows. Sources without a section are
+unchanged.

packages/api/src/mcp/__tests__/sources.test.ts

@@ -78,6 +78,7 @@ describe('MCP Source Tools', () => {
       traceIdExpression: 'TraceId',
       connection: connection._id,
       name: 'Logs',
+      section: 'Billing',
     });
 
     const context: McpContext = {
@@ -149,6 +150,19 @@ describe('MCP Source Tools', () => {
       expect(log.keyColumns).toHaveProperty('body');
     });
 
+    it('includes a source section when set and omits it when unset', async () => {
+      const result = await callTool(client, 'clickstack_list_sources');
+      const output = JSON.parse(getFirstText(result));
+
+      const log = output.sources.find((s: any) => s.kind === SourceKind.Log);
+      expect(log.section).toBe('Billing');
+
+      const trace = output.sources.find(
+        (s: any) => s.kind === SourceKind.Trace,
+      );
+      expect(trace.section).toBeUndefined();
+    });
+
     it('should return empty sources for a team with no sources', async () => {
       await client.close();
       await server.clearDBs();
@@ -222,6 +236,24 @@ describe('MCP Source Tools', () => {
       });
     });
 
+    it('includes the source section when set and omits it when unset', async () => {
+      const withSection = await callTool(client, 'clickstack_describe_source', {
+        sourceId: logSource._id.toString(),
+      });
+      expect(JSON.parse(getFirstText(withSection)).source.section).toBe(
+        'Billing',
+      );
+
+      const withoutSection = await callTool(
+        client,
+        'clickstack_describe_source',
+        { sourceId: traceSource._id.toString() },
+      );
+      expect(
+        JSON.parse(getFirstText(withoutSection)).source.section,
+      ).toBeUndefined();
+    });
+
     it('should include map attribute keys', async () => {
       const result = await callTool(client, 'clickstack_describe_source', {
         sourceId: traceSource._id.toString(),

packages/api/src/mcp/tools/sources/describeSource.ts

@@ -58,6 +58,10 @@ async function describeSourceSchema(
     timestampColumn: source.timestampValueExpression,
   };
 
+  if (source.section) {
+    meta.section = source.section;
+  }
+
   if (
     'eventAttributesExpression' in source &&
     source.eventAttributesExpression

packages/api/src/mcp/tools/sources/listSources.ts

@@ -44,6 +44,10 @@ export function registerListSources(
           timestampColumn: s.timestampValueExpression,
         };
 
+        if (s.section) {
+          meta.section = s.section;
+        }
+
         if ('eventAttributesExpression' in s && s.eventAttributesExpression) {
           meta.eventAttributesColumn = s.eventAttributesExpression;
         }