generate_indexer

THE RISK

Medium Risk

Why generate_indexer needs a policy

This tool generates code/configuration artifacts (a subgraph definition) for indexing blockchain events. It creates new files/code rather than executing commands or deleting data. The output is a reversible code generation artifact. Severity is medium because generated indexer code could be deployed to production infrastructure, but the tool itself only produces code, not executes it.

From the tool's definition Generate a The Graph subgraph for indexing Arbitrum smart contract events. Supports ERC20, ERC721, DeFi, and custom event patterns.

Documented attack patterns abuse exactly the kind of access generate_indexer gives an agent:

POLICY

How to control generate_indexer

PolicyLayer is an MCP gateway — it sits between your AI agents and ARBuilder, and nothing reaches the server without passing your rules. This is the rule we recommend for generate_indexer:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "generate_indexer": {
      "limits": [
        {
          "counter": "generate_indexer_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

generate_indexer stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.

Create a free account and register ARBuilder — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

LIMIT THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

More ARBuilder tools

Execute orchestrate_orbit Scaffold a complete Orbit chain deployment project with all scripts, configuration, and do Execute generate_orbit_deployment Generate deployment code for Orbit chains. Supports rollup deployment (createRollup), toke Write generate_backend Generate a Web3 backend using NestJS or Express with viem integration for Arbitrum. Includ Write generate_bridge_code Generate TypeScript code for bridging ETH or ERC20 tokens between L1, L2, and L3 (Orbit ch Write generate_frontend Generate a Next.js frontend with wagmi, RainbowKit, and DaisyUI for Arbitrum dApps. Includ Write generate_messaging_code Generate TypeScript code for Arbitrum cross-chain messaging. Supports L1->L2 messaging via Write generate_oracle Generate Chainlink oracle integration code for Arbitrum. Supports Price Feeds, VRF (random Write generate_orbit_config Generate configuration code for Orbit chain deployment. Supports chain config, AnyTrust DA

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Argument validation → Checking tool call arguments against schema and policy before they run.
Scoped token → Per-person credentials that grant a defined subset of servers and tools.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about generate_indexer

What does the generate_indexer tool do? +

Generate a The Graph subgraph for indexing Arbitrum smart contract events. Supports ERC20, ERC721, DeFi, and custom event patterns. It is categorised as a Write tool in the ARBuilder MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on generate_indexer? +

Register the ARBuilder MCP server in PolicyLayer and add a rule for generate_indexer: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches ARBuilder. Nothing to install.

What risk level is generate_indexer? +

generate_indexer is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit generate_indexer? +

Yes. Add a rate_limit block to the generate_indexer rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.

How do I block generate_indexer completely? +

Set action: deny in the PolicyLayer policy for generate_indexer. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.

What MCP server provides generate_indexer? +

generate_indexer is provided by the ARBuilder MCP server (quantum3-labs/arbuilder). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every ARBuilder tool call.

Start from ARBuilder, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →