Add Signet signing integration example

integrations/signet-signing/README.md

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+# CrewAI + Signet: Signed Tool Calls with Audit Trail
+
+This example shows how to add Ed25519 cryptographic signing to every
+CrewAI tool call, producing a tamper-evident audit log.
+
+## Why
+
+- Prove which agent called which tool, with what parameters, and when
+- Detect log tampering via SHA-256 hash chain
+- Comply with SOC 2 / HIPAA audit requirements for AI agent actions
+
+## Setup
+
+```bash
+pip install -r requirements.txt
+```
+
+## Run
+
+```bash
+python main.py
+```
+
+## Verify the audit trail
+
+```bash
+signet audit --since 1h
+signet audit --verify
+signet verify --chain
+```
+
+## How it works
+
+Signet hooks into CrewAI's `before_tool_use` / `after_tool_use` callbacks.
+Every tool invocation is signed with the agent's Ed25519 key and appended
+to a local hash-chained JSONL log at `~/.signet/audit/`.
+
+No infrastructure required. No network calls. Pure local crypto.
+
+## Learn more
+
+- [Signet GitHub](https://github.com/Prismer-AI/signet)
+- [PyPI: signet-auth](https://pypi.org/project/signet-auth/)

integrations/signet-signing/main.py

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+"""CrewAI + Signet: Sign every tool call with Ed25519."""
+
+from crewai import Agent, Crew, Task
+from crewai.tools import tool
+from signet_auth import SigningAgent
+from signet_auth.crewai import install_hooks, uninstall_hooks, get_receipts
+
+
+@tool("search")
+def search_tool(query: str) -> str:
+    """Search for information."""
+    return f"Results for: {query}"
+
+
+@tool("write_file")
+def write_tool(filename: str, content: str) -> str:
+    """Write content to a file."""
+    return f"Written to {filename}"
+
+
+def main():
+    # 1. Create a Signet identity
+    signer = SigningAgent.create("crew-bot", owner="demo", unencrypted=True)
+
+    # 2. Install signing hooks (3 lines!)
+    install_hooks(signer, audit=True)
+
+    # 3. Run your crew as usual
+    researcher = Agent(
+        role="Researcher",
+        goal="Find information about AI agent security",
+        backstory="You are a security researcher.",
+        tools=[search_tool],
+    )
+
+    writer = Agent(
+        role="Writer",
+        goal="Write a summary of the research",
+        backstory="You are a technical writer.",
+        tools=[write_tool],
+    )
+
+    task1 = Task(
+        description="Research MCP server security best practices",
+        expected_output="A list of security recommendations",
+        agent=researcher,
+    )
+
+    task2 = Task(
+        description="Write a summary of the security research",
+        expected_output="A written summary",
+        agent=writer,
+    )
+
+    crew = Crew(agents=[researcher, writer], tasks=[task1, task2])
+    crew.kickoff()
+
+    # 4. Check signed receipts
+    receipts = get_receipts()
+    print(f"\n{'='*60}")
+    print(f"Signed {len(receipts)} tool calls:")
+    for r in receipts:
+        print(f"  {r.ts}  {r.action.tool}  sig={r.sig[:30]}...")
+
+    # 5. Clean up
+    uninstall_hooks()
+
+    print(f"\nVerify with: signet audit --since 1h --verify")
+
+
+if __name__ == "__main__":
+    main()

integrations/signet-signing/requirements.txt

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+crewai>=0.80
+signet-auth>=0.4.0