Add set_output tool (#205)

mcp/README.md

@@ -154,11 +154,45 @@ await mcp.call("gh_pullfrog/reply_to_review_comment", {
 });
 ```
 
+### output tools
+
+#### `set_output`
+set the action output for consumption by subsequent workflow steps. useful when pullfrog is used as a step in a user-defined CI workflow (e.g., generating release notes).
+
+**parameters:**
+- `value` (string): the output value to expose
+
+**returns:**
+- `success`: true on success
+
+the value will be available as the `result` output of the action, accessible via `${{ steps.<step-id>.outputs.result }}`.
+
+**example:**
+```typescript
+// when generating content for downstream consumption
+await mcp.call("gh_pullfrog/set_output", {
+  value: "## Release Notes\n\n- Added new feature X\n- Fixed bug Y"
+});
+```
+
+**usage in workflow:**
+```yaml
+- uses: pullfrog/pullfrog@v1
+  id: notes
+  with:
+    prompt: "Generate release notes for v2.0.0"
+
+- uses: softprops/action-gh-release@v1
+  with:
+    body: ${{ steps.notes.outputs.result }}
+```
+
 ### other tools
 
 see individual files for documentation on other tools:
 - `comment.ts` - create, edit, and update comments
 - `issue.ts` - create issues
+- `output.ts` - set action output for workflow consumption
 - `pr.ts` - create pull requests
 - `prInfo.ts` - get pull request information
 - `review.ts` - create pull request reviews

mcp/output.ts

@@ -0,0 +1,20 @@
+import { type } from "arktype";
+import type { ToolContext } from "./server.ts";
+import { execute, tool } from "./shared.ts";
+
+export const SetOutputParams = type({
+  value: type.string.describe("the output value to expose as a GitHub Action output"),
+});
+
+export function SetOutputTool(ctx: ToolContext) {
+  return tool({
+    name: "set_output",
+    description:
+      "Set the action output for consumption by subsequent workflow steps. The value will be available as the 'result' output of the action.",
+    parameters: SetOutputParams,
+    execute: execute(async (params) => {
+      ctx.toolState.output = params.value;
+      return { success: true };
+    }),
+  });
+}

mcp/server.ts

@@ -32,6 +32,7 @@ export interface ToolState {
   progressCommentId: number | null;
   lastProgressBody?: string;
   wasUpdated?: boolean;
+  output?: string;
 }
 
 import type { ResolveRunResult } from "../utils/workflow.ts";
@@ -85,6 +86,7 @@ import { GetIssueCommentsTool } from "./issueComments.ts";
 import { GetIssueEventsTool } from "./issueEvents.ts";
 import { IssueInfoTool } from "./issueInfo.ts";
 import { AddLabelsTool } from "./labels.ts";
+import { SetOutputTool } from "./output.ts";
 import { CreatePullRequestTool } from "./pr.ts";
 import { PullRequestInfoTool } from "./prInfo.ts";
 import { CreatePullRequestReviewTool } from "./review.ts";
@@ -179,6 +181,7 @@ export async function startMcpHttpServer(
     CommitFilesTool(ctx),
     PushBranchTool(ctx),
     UploadFileTool(ctx),
+    SetOutputTool(ctx),
   ];
 
   // only add BashTool when bash is "restricted"