github-action.yml

name: Facet tool surface on PR

# Drop this into .github/workflows/facet-surface.yml
# On each PR, routes MCP tools for the PR's task and posts the planned surface
# as a comment — gives your code-review bot the right tool subset automatically.

on:
  pull_request:
    types: [opened, synchronize]

jobs:
  facet-surface:
    runs-on: ubuntu-latest
    permissions:
      pull-requests: write
      contents: read

    steps:
      - uses: actions/checkout@v4

      - uses: actions/setup-node@v4
        with:
          node-version: '20'

      - name: Get PR task description
        id: pr
        env:
          PR_TITLE: ${{ github.event.pull_request.title }}
          PR_BODY: ${{ github.event.pull_request.body }}
        run: |
          TASK="${PR_TITLE}: ${PR_BODY}"
          echo "task=${TASK}" >> $GITHUB_OUTPUT

      - name: Route tool surface for PR task
        id: surface
        run: |
          # Run facet plan with your manifest file (update path as needed)
          RESULT=$(npx -y @kioie/facet plan "${{ steps.pr.outputs.task }}" \
            --manifest ./tools.json \
            --budget 6000 \
            --json)
          echo "result<<EOF" >> $GITHUB_OUTPUT
          echo "$RESULT" >> $GITHUB_OUTPUT
          echo "EOF" >> $GITHUB_OUTPUT

      - name: Post tool surface as PR comment
        uses: actions/github-script@v7
        with:
          script: |
            const result = JSON.parse(`${{ steps.surface.outputs.result }}`);
            const selected = result.selected
              .map(t => `- \`${t.name}\``)
              .join('\n');
            const deferred = result.deferred
              .slice(0, 8)
              .map(t => `\`${t.name}\``)
              .join(', ');
            const savings = result.savingsPercent.toFixed(0);

            await github.rest.issues.createComment({
              owner: context.repo.owner,
              repo: context.repo.repo,
              issue_number: context.issue.number,
              body: [
                '## Facet tool surface',
                '',
                `**Task:** ${result.task}`,
                `**Tokens:** ${result.tokensAfter.toLocaleString()} / ${result.tokensBefore.toLocaleString()} (${savings}% saved)`,
                `**Selected:** ${result.selected.length} tools · **Deferred:** ${result.deferred.length} tools`,
                '',
                '### Selected tools',
                selected,
                '',
                `**Deferred:** ${deferred}${result.deferred.length > 8 ? ` +${result.deferred.length - 8} more` : ''}`,
                '',
                '*Generated by [Facet](https://github.com/kioie/facet) — task-aware MCP tool surface routing*'
              ].join('\n')
            });