Name: Datumline Agent Guard
Author: datumline

An independent verifier for AI agent work. An agent says a job is COMPLETED; agent-guard checks the artifacts it claims to have produced and returns a verdict. A completion claim with a missing artifact is reported as FALSE_DONE, not as a pass.

Standard library only, no dependencies. It imports nothing from the runtime it audits, so it can contradict that runtime.

Install

bash

pip install datumline-agent-guard

CLI

bash

agent-guard manifest.json          # human-readable receipt
agent-guard manifest.json --json   # machine-readable receipt

Exit code is 0 only on VERIFIED; every other verdict exits 1 (bad input exits 2), so it can gate CI or an agent loop.

Manifest

json

{
  "job": "WO-123",
  "claimed_status": "COMPLETED",
  "artifacts": [
    {"type": "file", "path": "out/report.md", "min_bytes": 200, "must_contain": ["## Findings"]},
    {"type": "json", "path": "out/feed.json", "required_keys": ["last_marked", "entries"]},
    {"type": "url",  "url": "https://example.com/feed.json", "status": 200, "must_contain": ["last_marked"]},
    {"type": "file", "path": "out/data.parquet", "sha256": "<hex>"}
  ]
}

Relative paths resolve against the current working directory.

Verdicts

Verdict	Meaning
`VERIFIED`	every artifact is present and passes every check
`FAILED`	an artifact is present but fails a check, or is absent without a completion claim
`FALSE_DONE`	`claimed_status` is COMPLETED / COMPLETE / DONE / VERIFIED and at least one artifact is absent
`UNVERIFIABLE`	the manifest asserts no artifacts; fail-closed, never green

Library

python

from datumline_agent_guard import verify, verify_file

receipt = verify({"claimed_status": "COMPLETED", "artifacts": [{"type": "file", "path": "out/report.md"}]})
if receipt["verdict"] != "VERIFIED":
    raise SystemExit(receipt["verdict"])

GitHub Action

Fail a workflow when an agent's "done" doesn't check out:

yaml

- uses: datumline/datumline-agent-guard@v0.2.0
  with:
    manifest: agent-output/manifest.json   # what the agent claims it produced
    # fail-on: false-done                  # only fail on FALSE_DONE (default: anything but VERIFIED)

The step installs this package from the action's own source (no network fetch), writes the receipt to the job summary, sets the verdict and receipt outputs, and exits non-zero unless the verdict is VERIFIED. It needs python3 3.9+ on the runner, which GitHub-hosted runners have.

MCP server

The same verifier as an MCP tool, verify_completion_claim, for Claude, ChatGPT, Copilot, Cursor or any MCP client. Standard library only, stdio transport.

json

{
  "mcpServers": {
    "agent-guard": { "command": "uvx", "args": ["datumline-agent-guard"] }
  }
}

Or pip install datumline-agent-guard and run datumline-agent-guard (alias agent-guard-mcp). The tool takes manifest (object) or manifest_path (string) and returns the receipt; anything other than "verdict": "VERIFIED" means not done. It reads the files and fetches the URLs the manifest names, and sends nothing anywhere else.

LangChain

bash

pip install "datumline-agent-guard[langchain]"

python

from datumline_agent_guard.langchain_tool import AgentGuardTool

tool = AgentGuardTool()  # name: agent_guard_verify
tool.invoke({"manifest": {"claimed_status": "COMPLETED", "artifacts": [{"type": "file", "path": "out/report.md"}]}})
# -> JSON receipt; anything other than "verdict": "VERIFIED" means not done

Give it to an agent as a tool, or call it yourself before accepting the agent's "done". It also takes manifest_path instead of manifest. It passes LangChain's standard tool tests (langchain-tests). Requires Python 3.10+; the core package needs only 3.9 and has no dependencies.

The same verifier ships inside the free, MIT-licensed Receipted Operator Claude Code plugin, which adds a receipt ledger, truthful statuses and a hook that refuses unreceipted "done". Datumline also publishes paid method kits at datumlinehq.gumroad.com.