# Show HN: Gnt, a company brain AI agents check before acting > Source: > Published: 2026-08-03 01:35:11+00:00 Run the setup below once and every agent your team runs has a **git-native rulebook** it has to check over **MCP** before it acts, approved the same way your code already is: a **merged pull request**. - Rules live in your repo as files and ship through normal PRs, not a dashboard click. - Agents call `check_action` over MCP before anything risky (a refund, a delete, a message to a customer) and get back an allow/block/escalate verdict. - Every rule traces back to the git file and the PR that approved it, so "why did the agent do that" always has a paper trail. Prefer not to run any of this yourself? The hosted version at [gntai.dev]does the same thing without you standing up a Postgres instance. *gnt prebrain scanning a repo, opening a PR, and getting it merged. A real terminal session, not a mockup.* ``` npm install -g @gnt-ai/cli gnt login gnt connect github gnt prebrain # merge the opened PR on GitHub. that merge is the approval ``` That merge lands a rule file in your connected repo, shaped like this: ``` your-repo/ └── rules/ ├── refund-approval-threshold.md └── contract-legal-cc.md ``` Each file is plain markdown with YAML frontmatter: ``` --- title: Never refund over $500 without a manager status: approved confidence: 0.91 owner_id: finance-team source_citations: [...] source: slack tags: [refunds, finance] last_validated_at: 2026-07-20 version: 1 superseded_by: null approved_by: jane@company.com approved_at: 2026-07-21T14:03:00Z created_at: 2026-07-18T09:12:00Z pr_number: 142 pr_url: https://github.com/your-org/your-repo/pull/142 --- Refunds over $500 need manager sign-off before they go out... ``` There's no captured transcript to show yet (see the gap noted at the bottom of this README). Here's the actual response shape a `check_action` call returns, straight from the tool's contract: ``` { "verdict": "blocked", "reason": "Refund exceeds the $500 threshold without manager sign-off (rules/refund-approval-threshold.md)", "cited_rules": [ { "id": "refund-approval-threshold", "title": "Never refund over $500 without a manager" } ], "rules_retrieved": 3 } ``` `verdict` is one of `allowed` , `blocked` , or `needs_human` . `needs_human` is the fail-closed default: no approved rule covers the action, retrieval failed, or the check couldn't complete. It never guesses. One MCP endpoint, five tools: | Tool | What it does | |---|---| `check_action` | Checks a described action against your approved rules before an agent takes it. Returns `allowed` , `blocked` , or `needs_human` with cited rules and a one-line reason. | `search_rules` | Semantic search over your org's approved rules, optionally filtered by tag. An empty list means no approved rule covers the query. | `get_rule` | Fetches one approved rule by id, with its provenance (who approved it, when, what it was cited from). | `list_skill_packs` | Lists every compiled skill pack version for your org, newest first. | `get_skill_pack` | Fetches a compiled skill pack's manifest and file list by id. | | Requirement | Check | Get it | |---|---|---| | Node >=22.13 | `node --version` | | | Method | Command | |---|---| | curl | `curl -fsSL gntai.dev/install.sh | sh` | | npm | `npm install -g @gnt-ai/cli` | gnt needs Node >=22.13. If the CLI fails to start with a version error, update Node first and confirm with `node --version` . ``` gnt login # sign in, store an API key locally gnt connect github # connect the repo your rules PRs open against gnt prebrain # scan sources, extract candidate rules, open PRs gnt review # review rules awaiting approval gnt status # show brain status gnt pull # download the latest skill pack gnt gaps # list uncovered queries with no approved rule ``` | Variable | Default | What it controls | |---|---|---| `GNT_API_URL` | `https://api.gntai.dev` | API endpoint the CLI and MCP calls hit | `GNT_WEB_URL` | `https://gntai.dev` | Web app used for `gnt login` 's browser step | `GNT_CONFIG_DIR` | `~/.gnt` | Where `credentials.json` and local config live | - No analytics or telemetry dependency in the CLI or the web app. `gnt prebrain` 's default extraction mode is cloud, not on-device: your source text goes straight to Anthropic's API (or Vercel AI Gateway with zero-data-retention, if you configure it), never to gnt's own servers. Fully on-device extraction needs`--mode local` against a local Ollama daemon.- The extracted rule candidates still get sent to gnt's API to open the PR. Raw source text stays off gnt's servers in cloud mode; the resulting rule text doesn't. - Rules live in your connected GitHub repo and in gnt's own database. The MCP tools read from gnt's store, not by cloning your repo on every call. - Self-hosting: `apps/api` only sends error data to Sentry if you set`SENTRY_DSN` yourself. Leave it unset and nothing goes out. **Who writes rules**: anyone with access to your connected repo, either through`gnt prebrain` (batch-extracted from real sources) or`gnt review` (hand-proposed).**How approval works**: merging the PR is the approval. There's no separate publish step.** What gets committed**:`rules/.md` files with the frontmatter shown above and a plain markdown body. Self-hosting:`gnt login` 's browser step has nowhere to land.`gnt login` opens a browser to a`/cli-login` page and polls the API for the resulting key — that page is served by the hosted product's web app, which isn't part of this repo. There's no CLI-only login flow (device code or otherwise) today, and no`gnt` command to set a key manually. Self-hosting this stack currently means building your own thin frontend for that one route (it just needs to complete the sign-in flow and hand the CLI a key). This is a real, open gap in the self-host path, not a config issue — closing it properly means adding a CLI-only login flow. A`ValueError: refusing to start: these settings still have their .env.example placeholder value...` `change-me-...` string is still sitting in`apps/api/.env` . The error names every offending field; generate a real value for each and retry. `store` fails to start with`GNT_STORE_INTERNAL_API_SECRET is not set` .`apps/store/.env` wasn't filled in, or wasn't picked up. Confirm the file exists at that exact path, not still named`.env.example` . Every store-to-api call gets rejected with 401 or 403, even though both services are up.`STORE_INTERNAL_API_SECRET` /`APPROVAL_SIGNING_SECRET` in`apps/api/.env` don't byte-for-byte match`GNT_STORE_INTERNAL_API_SECRET` /`GNT_APPROVAL_SIGNING_SECRET` in`apps/store/.env` . This fails closed by design. Regenerate both pairs so the two files agree. A rule fails to save with an embedding or rerank error.`apps/store/.env` is missing`ZEROENTROPY_API_KEY` , or it's still empty. Get a real one from zeroentropy.dev. ``` gnt login gnt logout gnt connect github, slack, notion-mcp, monday-mcp, linear-mcp, jira-mcp, sentry-mcp, granola-mcp, zoom-mcp, figma, datadog, gitlab-threads, hubspot, airtable, openclaw, hermes gnt disconnect gnt status gnt billing gnt review gnt pull gnt gaps gnt prebrain scan local sources, extract candidate rules, open batched draft PRs (~60 flags for source paths and extraction mode, see `gnt prebrain --help`; --mode cloud|local, cloud is the default) gnt stale gnt keys list|create|revoke|rotate gnt webhook list|create|revoke gnt org show|rename|invite|remove ``` - Self-hosting walkthrough, including the production-hardening path: `docs/self-hosting/README.md` - Security policy: `SECURITY.md` Copyright © 2026 gnt.ai. Licensed under Apache-2.0 — see [ LICENSE](/gnt-ai/gnt/blob/main/LICENSE) for the terms and [for the trademark rule on forks.](/gnt-ai/gnt/blob/main/NOTICE) `NOTICE` Self-hosting gnt costs you nothing, forever — clone it, run `docker compose up` , bring your own keys. What we sell is the part self-hosting doesn't give you: hosting at [gntai.dev](https://gntai.dev), managed OAuth connectors (GitHub, Slack, Linear, Notion, Zendesk — no app-approval process on your end), and usage-based AI features. If you'd rather run it yourself, that's a fully supported, fully free path, not a crippled trial of the real thing. See [ CONTRIBUTING.md](/gnt-ai/gnt/blob/main/CONTRIBUTING.md) for dev setup and how to open a PR. Every commit needs a `Signed-off-by` trailer (`git commit -s` ), the [Developer Certificate of Origin](https://developercertificate.org/)instead of a CLA. No separate form, just the flag.