Vizier Guard

Deterministic authorization and security guard for AI agent actions with signed receipts.

Quick Install

Automated & IDE Setup

Copy the AI prompt to install this server into Claude Code, Cursor, or another agent — or use 1-click editor setup below.

One-click editor setup isn’t available for this listing yet — we don’t have a confirmed install command, and we’d rather show nothing than point your editor at the wrong package or host. Follow the project’s own setup instructions, linked above.

Manual Client & Custom JSON ConfigExpand JSON ▾

No confirmed setup config for this listing yet. We only publish a config block when the install details come from the project itself — its README, its docs, or a verified owner. We haven’t found those for Vizier Guard, and we’d rather show nothing than a guess you’d paste into your client. Follow the project’s own setup instructions for the current steps.

Documentation Overview

Vizier

Check an AI agent's proposed action against a policy before it calls a tool that can change the world.

Vizier is for developers running agents that can call tools, send messages, change data, or spend money. Put its SDK or MCP proxy between the agent and the tool: it asks a deterministic policy service to ALLOW, BLOCK, or route for human REVIEW, and records a receipt. A response is not proof of user consent unless the authority behind it is verified; see signed delegation grants.

One-minute tour: open the live playground, choose an allowed action, then try BLOCK_AMOUNT and BLOCK_TARGET. The playground uses example policies and data; it does not connect to your bank or modify a real account. The point is to see where the stop occurs before wiring an agent to an external tool.

Try it in code: wrap an MCP server or use the Python SDK. Field reference · Threat model · OpenAPI.

What it does not do: Vizier does not execute the protected action for you. An unverified caller-supplied authority field is an assertion, not a signed grant. Integrate a guard at the tool boundary and check fail-closed behavior before relying on it. This is experimental v0.5.5, not an independent security certification. The @vizier npm scope is not currently published; install the release archives. The MCP proxy is a separate package, not a hosted MCP wrapper of every agent.

How it fits together: agent -> Python/TypeScript guard or MCP proxy -> deterministic policy service on Cloudflare Workers -> decision and receipt -> protected tool only on an authorized allow path. The architecture diagram and technical reference below retain the integration details.

License: MIT. Questions and integration feedback: GitHub issues.

🏛️ Architecture

mermaid

flowchart TD
    subgraph Agents["AI Agent Runtimes"]
        A1["Python Agent (LangChain / CrewAI / AutoGen)"]
        A2["MCP Client (Claude / Cursor / Tools)"]
        A3["TypeScript / Node.js Agent"]
    end

    subgraph Guards["Vizier Enforcement Boundary"]
        G1["@vizier_guard / Python SDK"]
        G2["@vizier/mcp-proxy CLI"]
        G3["@vizier/sdk (TypeScript)"]
    end

    subgraph Kernel["Cloudflare Workers Global Edge"]
        K["Vizier Deterministic Kernel (/v1/verify)"]
        P["Policy Engine: Limits, Targets, Roles, Grants"]
        D1["D1 Audit Ledger & Cryptographic Receipts"]
    end

    subgraph Targets["Protected External Side-Effects"]
        T1["Payment / Financial APIs"]
        T2["Database Writes & Deletions"]
        T3["Worker / Infrastructure Deployments"]
        T4["External Message Dispatch"]
    end

    A1 --> G1
    A2 --> G2
    A3 --> G3

    G1 -->|"POST /v1/verify"| K
    G2 -->|"POST /v1/verify"| K
    G3 -->|"POST /v1/verify"| K

    K --> P
    P --> D1

    G1 -.->|"Decision: ALLOW"| T1
    G2 -.->|"Decision: ALLOW"| T2
    G3 -.->|"Decision: ALLOW"| T3

    P -.->|"Decision: BLOCK / REVIEW"| G1
    P -.->|"Decision: BLOCK / REVIEW"| G2
    P -.->|"Decision: BLOCK / REVIEW"| G3

The decision path is strictly deterministic — no non-deterministic LLMs in the critical decision loop. It checks delegated actions, principal identity, amount limits, targets, sensitive operations, and authenticated integration boundaries. Every response includes policy results and a tamper-proof SHA-256 canonical receipt hash.

Status: experimental v0.5.5, deployed on Cloudflare Workers edge. Since v0.3.0, authority can be proved rather than asserted: a principal signs a delegation grant, Vizier verifies it against a registered public key, and the receipt records authority provenance. Read the threat model before placing this service in an execution path.

🌐 Public Surfaces

Edge Worker: https://vizier.vassiliy-lakhonin.workers.dev
Action Playground: https://vizier.vassiliy-lakhonin.workers.dev/playground
Live Field Reference: https://vizier.vassiliy-lakhonin.workers.dev/docs
OpenAPI 3.1 Contract: https://vizier.vassiliy-lakhonin.workers.dev/openapi.json
AI Discovery Catalog: https://vizier.vassiliy-lakhonin.workers.dev/.well-known/ai-catalog.json
MCP Server Manifest: https://vizier.vassiliy-lakhonin.workers.dev/.well-known/mcp.json
MCP Registry Entry: io.github.vassiliylakhonin/vizier
Agent Card: https://vizier.vassiliy-lakhonin.workers.dev/.well-known/agent-card.json
Public Key Set (JWKS): https://vizier.vassiliy-lakhonin.workers.dev/.well-known/jwks.json

🚀 Quickstarts

1. Python SDK (`vizier-guard`)

Zero external dependencies (Python standard library only):

Terminal

pip install vizier-guard

server.ts

from vizier import VizierClient, vizier_guard

client = VizierClient(
    base_url="https://vizier.vassiliy-lakhonin.workers.dev",
    api_key="your-api-key"
)

# Protect any function or tool:
@vizier_guard(
    client=client,
    action_type="purchase",
    max_amount=500.0,
    currency="USD",
    allowed_targets=["supplier.example"]
)
def execute_order(amount: float, target: str):
    # Runs ONLY if Vizier decision is ALLOW
    return {"status": "success", "amount": amount}

execute_order(amount=450.0, target="supplier.example")   # Allowed
execute_order(amount=1200.0, target="supplier.example")  # Raises ActionBlockedError

LangChain / LangGraph & CrewAI:

server.ts

from vizier.integrations.langchain import VizierLangChainToolGuard
from vizier.integrations.crewai import VizierCrewAIToolGuard

# LangChain / LangGraph
safe_tool = VizierLangChainToolGuard(
    tool=my_search_tool,
    client=client,
    allowed_actions=["search"],
    max_amount=0.0
)

# CrewAI
safe_crew_tool = VizierCrewAIToolGuard(
    tool=my_payment_tool,
    client=client,
    max_amount=250.0
)

Human-in-the-Loop (Telegram / CLI / Webhooks) & Async:

server.ts

from vizier import AsyncVizierClient, vizier_guard, TelegramHITLHandler

# Interactive approval buttons via Telegram Bot when decision is REVIEW
telegram_approver = TelegramHITLHandler(
    bot_token=os.environ["TELEGRAM_BOT_TOKEN"],
    chat_id=os.environ["TELEGRAM_CHAT_ID"]
)

@vizier_guard(
    client=AsyncVizierClient(),
    action_type="transfer_funds",
    hitl_handler=telegram_approver
)
async def transfer(amount: float, target: str):
    # Executes ONLY if human operator clicks [Approve] in Telegram
    return await bank_api.send(amount, target)

MCP Server for Claude Desktop & Cursor:

Equip Claude Desktop or Cursor with deterministic guardrails (vizier_screen_action, vizier_verify_receipt, vizier_check_policy):

config.json

{
  "mcpServers": {
    "vizier": {
      "command": "uvx",
      "args": ["vizier-guard", "mcp"],
      "env": {
        "VIZIER_BASE_URL": "https://vizier.vassiliy-lakhonin.workers.dev",
        "VIZIER_API_KEY": "your-vizier-api-key"
      }
    }
  }
}

2. MCP Enforcement Proxy CLI

Wrap any local or remote MCP server with deterministic authorization:

Terminal

npm install https://github.com/vassiliylakhonin/vizier/releases/download/v0.5.5/vizier-sdk-0.5.5.tgz https://github.com/vassiliylakhonin/vizier/releases/download/v0.5.5/vizier-mcp-proxy-0.5.5.tgz
npx --no-install vizier-mcp-proxy \
  --upstream http://localhost:3000/mcp \
  --tools "query_db,execute_command,fetch_api" \
  --vizier https://vizier.vassiliy-lakhonin.workers.dev \
  --api-key $VIZIER_API_KEY

3. TypeScript SDK (`@vizier/sdk`)

Terminal

npm install https://github.com/vassiliylakhonin/vizier/releases/download/v0.5.5/vizier-sdk-0.5.5.tgz

server.ts

import { Vizier } from "@vizier/sdk";

const vizier = new Vizier({
  baseUrl: "https://vizier.vassiliy-lakhonin.workers.dev",
  apiKey: process.env.VIZIER_API_KEY,
});

const decision = await vizier.verify({
  agent: { id: "agent-01", owner: "acme-corp" },
  principal: { id: "acme-corp" },
  action: {
    type: "purchase",
    target: "supplier.example",
    parameters: { amount: 820, currency: "USD" }
  },
  authority: {
    allowed_actions: ["purchase"],
    constraints: { max_amount: 1000, currency: "USD" }
  },
  context: { source: "rest" }
});

if (decision.decision === "ALLOW") {
  // Execute protected operation
}

4. Direct HTTP / cURL

Read the full README →View source on GitHub →

Related MCP Servers

View all in Developer Tools View all alternatives

Reviews

No reviews yet — be the first to share how this listing worked for you.

Frequently Asked Questions about Vizier Guard

We don't have a confirmed install command for Vizier Guard yet, so we don't publish a generated one — a guessed package name would point at the wrong package or none at all. Follow the project's own README or setup instructions (https://github.com/vassiliylakhonin/vizier) for the current steps.

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Technical Specs & Signals

CategoryDeveloper Tools

27Quality signal: Emerging · 27/100How this signal is calculated ▾

Server availabilityNot measured

Not scored for repo-hosted servers — we can't reach the running server, only its GitHub page. Hosted MCP endpoints are health-checked live.

Verified ownership8/20

Documentation & tools11/30

Adoption & activity1/15

Community engagement0/10

A guidance signal from public completeness & health data — not a user rating. New listings start lower and rise as they add docs, get verified, and grow adoption. Signals we can't observe for a listing are skipped, not counted against it.

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More in 💻 Developer Tools →Best MCP servers for Developers →Alternatives to Vizier Guard →Install in Claude Desktop Install in Cursor Install in VS Code Setup guides for all 13 MCP clients

Vizier Guard

Deterministic authorization and security guard for AI agent actions with signed receipts.

Quick Install

Automated & IDE Setup

Copy the AI prompt to install this server into Claude Code, Cursor, or another agent — or use 1-click editor setup below.

Manual Client & Custom JSON ConfigExpand JSON ▾

Documentation Overview

Vizier

Check an AI agent's proposed action against a policy before it calls a tool that can change the world.

Try it in code: wrap an MCP server or use the Python SDK. Field reference · Threat model · OpenAPI.

License: MIT. Questions and integration feedback: GitHub issues.

🏛️ Architecture

mermaid

flowchart TD
    subgraph Agents["AI Agent Runtimes"]
        A1["Python Agent (LangChain / CrewAI / AutoGen)"]
        A2["MCP Client (Claude / Cursor / Tools)"]
        A3["TypeScript / Node.js Agent"]
    end

    subgraph Guards["Vizier Enforcement Boundary"]
        G1["@vizier_guard / Python SDK"]
        G2["@vizier/mcp-proxy CLI"]
        G3["@vizier/sdk (TypeScript)"]
    end

    subgraph Kernel["Cloudflare Workers Global Edge"]
        K["Vizier Deterministic Kernel (/v1/verify)"]
        P["Policy Engine: Limits, Targets, Roles, Grants"]
        D1["D1 Audit Ledger & Cryptographic Receipts"]
    end

    subgraph Targets["Protected External Side-Effects"]
        T1["Payment / Financial APIs"]
        T2["Database Writes & Deletions"]
        T3["Worker / Infrastructure Deployments"]
        T4["External Message Dispatch"]
    end

    A1 --> G1
    A2 --> G2
    A3 --> G3

    G1 -->|"POST /v1/verify"| K
    G2 -->|"POST /v1/verify"| K
    G3 -->|"POST /v1/verify"| K

    K --> P
    P --> D1

    G1 -.->|"Decision: ALLOW"| T1
    G2 -.->|"Decision: ALLOW"| T2
    G3 -.->|"Decision: ALLOW"| T3

    P -.->|"Decision: BLOCK / REVIEW"| G1
    P -.->|"Decision: BLOCK / REVIEW"| G2
    P -.->|"Decision: BLOCK / REVIEW"| G3

🌐 Public Surfaces

Edge Worker: https://vizier.vassiliy-lakhonin.workers.dev
Action Playground: https://vizier.vassiliy-lakhonin.workers.dev/playground
Live Field Reference: https://vizier.vassiliy-lakhonin.workers.dev/docs
OpenAPI 3.1 Contract: https://vizier.vassiliy-lakhonin.workers.dev/openapi.json
AI Discovery Catalog: https://vizier.vassiliy-lakhonin.workers.dev/.well-known/ai-catalog.json
MCP Server Manifest: https://vizier.vassiliy-lakhonin.workers.dev/.well-known/mcp.json
MCP Registry Entry: io.github.vassiliylakhonin/vizier
Agent Card: https://vizier.vassiliy-lakhonin.workers.dev/.well-known/agent-card.json
Public Key Set (JWKS): https://vizier.vassiliy-lakhonin.workers.dev/.well-known/jwks.json

🚀 Quickstarts

1. Python SDK (`vizier-guard`)

Zero external dependencies (Python standard library only):

Terminal

pip install vizier-guard

server.ts

from vizier import VizierClient, vizier_guard

client = VizierClient(
    base_url="https://vizier.vassiliy-lakhonin.workers.dev",
    api_key="your-api-key"
)

# Protect any function or tool:
@vizier_guard(
    client=client,
    action_type="purchase",
    max_amount=500.0,
    currency="USD",
    allowed_targets=["supplier.example"]
)
def execute_order(amount: float, target: str):
    # Runs ONLY if Vizier decision is ALLOW
    return {"status": "success", "amount": amount}

execute_order(amount=450.0, target="supplier.example")   # Allowed
execute_order(amount=1200.0, target="supplier.example")  # Raises ActionBlockedError

LangChain / LangGraph & CrewAI:

server.ts

from vizier.integrations.langchain import VizierLangChainToolGuard
from vizier.integrations.crewai import VizierCrewAIToolGuard

# LangChain / LangGraph
safe_tool = VizierLangChainToolGuard(
    tool=my_search_tool,
    client=client,
    allowed_actions=["search"],
    max_amount=0.0
)

# CrewAI
safe_crew_tool = VizierCrewAIToolGuard(
    tool=my_payment_tool,
    client=client,
    max_amount=250.0
)

Human-in-the-Loop (Telegram / CLI / Webhooks) & Async:

server.ts

from vizier import AsyncVizierClient, vizier_guard, TelegramHITLHandler

# Interactive approval buttons via Telegram Bot when decision is REVIEW
telegram_approver = TelegramHITLHandler(
    bot_token=os.environ["TELEGRAM_BOT_TOKEN"],
    chat_id=os.environ["TELEGRAM_CHAT_ID"]
)

@vizier_guard(
    client=AsyncVizierClient(),
    action_type="transfer_funds",
    hitl_handler=telegram_approver
)
async def transfer(amount: float, target: str):
    # Executes ONLY if human operator clicks [Approve] in Telegram
    return await bank_api.send(amount, target)

MCP Server for Claude Desktop & Cursor:

Equip Claude Desktop or Cursor with deterministic guardrails (vizier_screen_action, vizier_verify_receipt, vizier_check_policy):

config.json

{
  "mcpServers": {
    "vizier": {
      "command": "uvx",
      "args": ["vizier-guard", "mcp"],
      "env": {
        "VIZIER_BASE_URL": "https://vizier.vassiliy-lakhonin.workers.dev",
        "VIZIER_API_KEY": "your-vizier-api-key"
      }
    }
  }
}

2. MCP Enforcement Proxy CLI

Wrap any local or remote MCP server with deterministic authorization:

Terminal

npm install https://github.com/vassiliylakhonin/vizier/releases/download/v0.5.5/vizier-sdk-0.5.5.tgz https://github.com/vassiliylakhonin/vizier/releases/download/v0.5.5/vizier-mcp-proxy-0.5.5.tgz
npx --no-install vizier-mcp-proxy \
  --upstream http://localhost:3000/mcp \
  --tools "query_db,execute_command,fetch_api" \
  --vizier https://vizier.vassiliy-lakhonin.workers.dev \
  --api-key $VIZIER_API_KEY

3. TypeScript SDK (`@vizier/sdk`)

Terminal

npm install https://github.com/vassiliylakhonin/vizier/releases/download/v0.5.5/vizier-sdk-0.5.5.tgz

server.ts

import { Vizier } from "@vizier/sdk";

const vizier = new Vizier({
  baseUrl: "https://vizier.vassiliy-lakhonin.workers.dev",
  apiKey: process.env.VIZIER_API_KEY,
});

const decision = await vizier.verify({
  agent: { id: "agent-01", owner: "acme-corp" },
  principal: { id: "acme-corp" },
  action: {
    type: "purchase",
    target: "supplier.example",
    parameters: { amount: 820, currency: "USD" }
  },
  authority: {
    allowed_actions: ["purchase"],
    constraints: { max_amount: 1000, currency: "USD" }
  },
  context: { source: "rest" }
});

if (decision.decision === "ALLOW") {
  // Execute protected operation
}

4. Direct HTTP / cURL

Read the full README →View source on GitHub →

Related MCP Servers

View all in Developer Tools View all alternatives

Reviews

No reviews yet — be the first to share how this listing worked for you.

Frequently Asked Questions about Vizier Guard

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<a href="https://allmcps.com/mcp/vizier-guard"><img src="https://allmcps.com/api/badge/vizier-guard?style=directory" alt="Vizier Guard on AllMCPs" /></a>

Technical Specs & Signals

CategoryDeveloper Tools

27Quality signal: Emerging · 27/100How this signal is calculated ▾

Server availabilityNot measured

Not scored for repo-hosted servers — we can't reach the running server, only its GitHub page. Hosted MCP endpoints are health-checked live.

Verified ownership8/20

Documentation & tools11/30

Adoption & activity1/15

Community engagement0/10

★ Spotlight Slot

Feature Your MCP Server

Get maximum visibility for your server across our directory, search results, and detail pages.

Spotlight Your Server

Own this project?

Free dofollow backlink: add your website and place the AllMCPs badge on it — no claim needed. We detect it automatically and keep it verified as long as the badge stays live.

Claim & get free dofollow

Share & Embed

Add our SVG badge (dark/light directory styles) or embeddable widget to your site.

Explore more

More in 💻 Developer Tools →Best MCP servers for Developers →Alternatives to Vizier Guard →Install in Claude Desktop Install in Cursor Install in VS Code Setup guides for all 13 MCP clients

Vizier Guard

Quick Install

Documentation Overview

Vizier

🏛️ Architecture

🌐 Public Surfaces

🚀 Quickstarts

1. Python SDK (vizier-guard)

LangChain / LangGraph & CrewAI:

Human-in-the-Loop (Telegram / CLI / Webhooks) & Async:

MCP Server for Claude Desktop & Cursor:

2. MCP Enforcement Proxy CLI

3. TypeScript SDK (@vizier/sdk)

4. Direct HTTP / cURL

Related MCP Servers

Reviews

Frequently Asked Questions about Vizier Guard

AllMCPs Directory Badge

Technical Specs & Signals

Feature Your MCP Server

Own this project?

Share & Embed

Explore more

Vizier Guard

Quick Install

Documentation Overview

Vizier

🏛️ Architecture

🌐 Public Surfaces

🚀 Quickstarts

1. Python SDK (vizier-guard)

LangChain / LangGraph & CrewAI:

Human-in-the-Loop (Telegram / CLI / Webhooks) & Async:

MCP Server for Claude Desktop & Cursor:

2. MCP Enforcement Proxy CLI

3. TypeScript SDK (@vizier/sdk)

4. Direct HTTP / cURL

Related MCP Servers

Reviews

Frequently Asked Questions about Vizier Guard

AllMCPs Directory Badge

Technical Specs & Signals

Feature Your MCP Server

Own this project?

Share & Embed

Explore more

1. Python SDK (`vizier-guard`)

3. TypeScript SDK (`@vizier/sdk`)

1. Python SDK (`vizier-guard`)

3. TypeScript SDK (`@vizier/sdk`)