create-custom-api

THE RISK

Medium Risk

Why create-custom-api needs a policy

This tool creates a new Custom API definition in Dataverse, which is a write operation that adds a new resource to the system. While reversible (can be deleted), Custom APIs are powerful extensibility points that could be exploited to expose unintended functionality, inject logic into business processes, or create attack vectors for privilege escalation or data exfiltration.

From the tool's definition Tool name 'create-custom-api' and description 'Create a new Custom API definition in Dataverse' indicate creation of a new resource in a business-critical platform.

Documented attack patterns abuse exactly the kind of access create-custom-api gives an agent:

POLICY

How to control create-custom-api

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

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "create-custom-api": {
      "limits": [
        {
          "counter": "create-custom-api_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

create-custom-api 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 PowerPlatform MCP — 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 PowerPlatform MCP tools

Destructive delete-security-role Delete a security role. Destructive — requires confirm: true to proceed. Destructive remove-security-role-privileges Remove privileges from a security role. Loops RemovePrivilegeRole — each privilege is remo Destructive replace-security-role-privileges Replace the entire set of privileges on a role with the supplied list (ReplacePrivilegesRo Execute cancel-flow-run Cancel a running or waiting flow run. Cannot cancel flows already in a terminal state (Suc Execute resubmit-flow-run Resubmit/retry a failed flow run using the original trigger inputs Execute publish-customizations Publish entity customizations or all customizations in Dataverse Write add-security-role-privileges Append privileges to a security role using AddPrivilegesRole. Existing privileges are pres Write add-solution-component Add a component to a Dataverse solution

All 66 PowerPlatform MCP tools →

Write tools on other servers

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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 create-custom-api

What does the create-custom-api tool do? +

Create a new Custom API definition in Dataverse. It is categorised as a Write tool in the PowerPlatform MCP MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on create-custom-api? +

Register the PowerPlatform MCP server in PolicyLayer and add a rule for create-custom-api: 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 PowerPlatform MCP. Nothing to install.

What risk level is create-custom-api? +

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

Can I rate-limit create-custom-api? +

Yes. Add a rate_limit block to the create-custom-api 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 create-custom-api completely? +

Set action: deny in the PolicyLayer policy for create-custom-api. 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 create-custom-api? +

create-custom-api is provided by the PowerPlatform MCP server (michsob/powerplatform-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every PowerPlatform MCP tool call.

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

CHECK YOUR STACK →