Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx agentmods add skills/google/adk-python/adk-architecturenpx skills add google/adk-python --skill adk-architecturegit clone --depth 1 https://github.com/google/adk-pythonWhat it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5 | $0.00157 | $0.01124 |
| Opus 5 | $0.00078 | $0.00562 |
| Sonnet 5 | $0.00031 | $0.00225 |
| Haiku 4.5 | $0.00016 | $0.00112 |
Grade A, and why
adk-architecture scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured yesterday.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 76 lines — stays where its author put it; the contents beside it link to each section on GitHub.
ADK Architecture
The runtime is a graph of nodes. BaseNode is the unit of execution.
Workflow is a node that schedules other nodes along declared edges.
NodeRunner executes exactly one node. Runner owns the invocation and the
session. Agents are nodes too — BaseAgent extends BaseNode.
A node communicates with its parent through a per-execution Context, and
with the session through Events it yields. Those are two separate channels:
ctx carries the result upward, events carry persistence and streaming.
Read the source before relying on any signature here. These notes drift; the
code does not. Paths below are relative to src/google/adk/.
Pick a reference
| Question | Reference |
|---|---|
| What must a node implement? What may it yield? Which config fields exist? | BaseNode |
| How does the graph schedule nodes, dedup dynamic children, propagate interrupts? | Workflow |
| How does a caller start an invocation? | Runner |
What is Agent, and which methods do I call on it? |
Agent |
| I am subclassing an agent — what do I override? | BaseAgent |
What is on an Event, and what may I assume about its lifetime? |
Event |
What does a node read and write on ctx? |
Context |
| Who creates the child Context, stamps events, retries, catches errors? | NodeRunner |
| Why are Runner, NodeRunner and Workflow three separate things? | Runner roles |
| How does a human-in-the-loop pause and resume work for one node? | Checkpoint and resume |
How does a whole workflow survive a pause, and what does is_resumable change? |
Workflow resumability |
| How are spans created, and what attributes do they carry? | Observability |
| Why does the model not see the raw event log? | LLM context orchestration |
| Is this change a breaking change? Where does a new export belong? | API principles |
What ships with it
14 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
- references/api-principles.md 1.9 KB
- references/architecture-checkpoint-resume.md 2.6 KB
- references/architecture-context.md 4.2 KB
- references/architecture-llm-context-orchestration.md 1.9 KB
- references/architecture-node-runner.md 4.4 KB
- references/architecture-observability.md 3.6 KB
- references/architecture-runner-roles.md 452 B
- references/architecture-workflow-resumability.md 7.7 KB
- references/interface-agent.md 2.0 KB
- references/interface-base-agent.md 2.0 KB
- references/interface-base-node.md 4.9 KB
- references/interface-event.md 3.0 KB
- references/interface-runner.md 1.7 KB
- references/interface-workflow.md 13 KB
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- yesterday First seen · 76 lines · 157 tokens per session scan A 10f510ec9911
adk-architecture is a skill published in the GitHub repository google/adk-python (21,331 stars, last pushed 2d ago), licensed Apache-2.0. It adds 157 tokens to every session and 1,124 once invoked, about $0.0008 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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