Medium Risk

api-merger

Merge multiple API responses into a single unified response keyed by a shared field.

Part of the Api Composition Gateway server.

api-merger can modify Api Composition Gateway data, with no limits today. PolicyLayer puts allow, deny, and rate-limit rules on every call. Live in minutes.

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AI agents use api-merger to create or modify resources in Api Composition Gateway. Write operations carry medium risk because an autonomous agent could trigger bulk unintended modifications. Rate limits prevent a single agent session from making hundreds of changes in rapid succession. Argument validation ensures the agent passes expected values.

Without a policy, an AI agent could call api-merger repeatedly, creating or modifying resources faster than any human could review. PolicyLayer's rate limiting ensures write operations happen at a controlled pace, and argument validation catches malformed or unexpected inputs before they reach Api Composition Gateway.

Write tools can modify data. A rate limit prevents runaway bulk operations from AI agents.

policy.json
{
  "version": "1",
  "default": "deny",
  "tools": {
    "api-merger": {
      "limits": [
        {
          "counter": "api-merger_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

See the full Api Composition Gateway policy for all 4 tools.

Get this rule live on your own Api Composition Gateway server in minutes. PolicyLayer enforces it on every call, before it runs.

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These attack patterns abuse exactly the kind of access api-merger gives an agent. Each links to the full case and the policy that stops it:

Browse the full MCP Attack Database →

Every attack above starts with a tool call. PolicyLayer checks each one against your policy first, so api-merger only ever does what you allow.

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Other write tools across the catalogue. The same approach applies to each: rate-limit and validate the arguments.

What does the api-merger tool do? +

Merge multiple API responses into a single unified response keyed by a shared field.. It is categorised as a Write tool in the Api Composition Gateway MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on api-merger? +

Register the Api Composition Gateway MCP server in PolicyLayer and add a rule for api-merger: 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 Api Composition Gateway. Nothing to install.

What risk level is api-merger? +

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

Can I rate-limit api-merger? +

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

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

api-merger is provided by the Api Composition Gateway MCP server (https://api.lazy-mac.com/api-composition-gateway/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Api Composition Gateway tool call.

Deterministic rules across all 4 Api Composition Gateway tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.

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