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A tool node fetches a raw PR diff from the GitHub API, then an agent summarizes the changes. Demonstrates how to chain an HTTP tool node with a downstream agent node using a real external API.
What it demonstrates
tool node with tool: http for external API calls- Template interpolation in HTTP headers (
{{ env.GITHUB_TOKEN }})
- Chaining a tool node to an agent node via an edge
- Passing fetched data through the workflow context to a downstream agent
Prerequisites
Set a GitHub personal access token with repo:read scope:
export GITHUB_TOKEN=ghp_...
Run it
sirenspec run docs/cookbook/pr-summarizer/workflow.yaml \
--input "Summarise this pull request for me."
url in workflow.yaml to match your repository and PR number:
https://api.github.com/repos/{owner}/{repo}/pulls/{number}
Workflow
docs/cookbook/pr-summarizer/workflow.yaml
version: "0.1"
agents:
summarizer:
model: "openai:gpt-4o-mini"
system: |
You are a senior software engineer reviewing a GitHub pull request.
You will be given the raw unified diff of the pull request.
Write a concise, developer-friendly summary covering what changed,
why the change is likely being made, and any notable risks.
Keep the summary under 200 words.
nodes:
fetch_diff:
type: tool
tool: http
config:
url: "https://api.github.com/repos/TJLSmith0831/sirenspec/pulls/1"
method: GET
headers:
Authorization: "Bearer {{ env.GITHUB_TOKEN }}"
Accept: "application/vnd.github.v3.diff"
User-Agent: "sirenspec/0.1"
timeout: 15
output_key: diff
summarize:
agent: summarizer
writes: output.summary
edges:
- from: fetch_diff
to: summarize
guardrails:
- injection
Graph
Next steps
Tool Nodes
Full HTTP and Python tool node documentation.
Blind Code Review
Multi-turn refinement: write, review, revise.
