MCP limits and errors - Square Cloud

Limits

The limits are per account and shared by all its MCP connections. Each layer applies on top of the previous one:

Requests to the MCP server. Up to 60 a minute per account, or your plan’s API rate limit if it is lower. They count apart from your API calls, so a busy agent never blocks your other integrations. Over it, requests answer 429 RATE_LIMITED for 60 seconds.
An account blocked on the API is blocked here too. While the account is over its API rate limit, the MCP server answers 429 RATE_LIMITED as well.
The tool budget: tool calls a minute, half your plan’s API rate and at most 60, since a tool call does much more work than a request.
Per-tool caps for the tools that read or write inside your application or query the edge network.
The per-tool limits of Cubic, the Square Cloud AI assistant. The MCP and Cubic share them, per account.

Layers 3, 4 and 5 answer with a TOOL_RATE_LIMITED tool result, described below.

Tools	Calls a minute	Pause once reached
All tools, `HOBBY-1`	15	60 s
All tools, `HOBBY-2`	30	60 s
All tools, `STANDARD-4` and above	60	60 s
`list_files`, `read_file`	20 each	60 s
`search_files`	3	120 s
`list_env_vars`	10	60 s
`create_file`, `edit_file`, `patch_file`, `rename_file`	10 each	120 s
`edit_config_file`	5	120 s
`delete_file`	5	180 s
`get_application_logs`	10	60 s
`get_application_status`	20	60 s
`get_metrics_history`	10	60 s
`get_network_analytics`, `get_network_errors`, `get_network_performance`, `get_network_logs`	5 each	60 s
`search_help_center`	4	60 s
`list_help_center`	2	60 s
`start_application`, `stop_application`, `restart_application`	10 each	120 s

Every tool call counts, including calls refused for a resource or for a scope that depends on the arguments (such as restart on set_env_vars).
On HOBBY-1, for example, the MCP never goes past 15 tool calls a minute, and your CLI, SDKs and bots keep the plan’s whole API rate.

TOOL_RATE_LIMITED

A tool over a limit doesn’t run. The answer is a regular tool result marked isError: true, not an HTTP error, so the connection keeps working:

{
  "ok": false,
  "code": "TOOL_RATE_LIMITED",
  "summary": "read_file did NOT run: this action is on a short safety cooldown. Continue with what you already have, and tell the user it can run again in about 60 seconds."
}

When the tool budget is the limit reached, the summary says too many AI actions in a short time and every tool waits; otherwise only that tool does. If the client calls the same tool again while it is still limited, that second refusal in a row answers TOOL_EXECUTION_FAILED instead, which tells the client to stop and you to wait a few minutes or use the dashboard.

Errors

HTTP errors

These come back as the HTTP status of the request, with a JSON body carrying code.

Status	Code	When	What to do
`401`	`ACCESS_DENIED`	No key, or the key is wrong, revoked or expired. The answer carries the OAuth challenge, so Claude and ChatGPT ask you to sign in again.	Reconnect the client, or create a new API key.
`403`	`ACCESS_DENIED`	A dashboard session token was sent instead of an API key.	Connect with OAuth or with an API key.
`403`	`MISSING_SCOPE`	The key doesn’t have the `mcp` scope. Also returned when a Claude or ChatGPT key is used on the REST API.	Create a key with `mcp`.
`403`	`UPGRADE_REQUIRED`	The account has no active plan.	Subscribe to or renew a plan.
`421`	`WRONG_HOST`	The request went to another Square Cloud address, such as `api.squarecloud.app`.	Use `https://mcp.squarecloud.app/mcp`.
`429`	`RATE_LIMITED`	Over the MCP server’s request limit, or the account is blocked by its API rate limit.	Wait a minute and slow the client down.
`400`	JSON-RPC error	An unsupported protocol version (`-32022`, with the supported list) or a malformed request.	Update the client.

While connecting

What you see	Why	What to do
`UNKNOWN_CLIENT` or `INVALID_REDIRECT_URI` on a page of `mcp.squarecloud.app`	Only Claude, with its published identity, and ChatGPT sign in with OAuth.	In Claude, choose Use Claude’s published identity. In other clients, connect with an API key.
`The account is at its API key limit`	The account already has 10 keys.	Revoke a key in your account security settings and connect again.
The consent page says the request expired	It lasts 10 minutes.	Start the connection again from the client.

Tool results

These come back inside a tool result, as code, next to a summary the client reads.

Code	Meaning	What to do
`SNAPSHOT_NOT_READY`	The safety snapshot taken before a deletion or restore is still being generated. Nothing ran.	The client tries again with the same arguments in about 2 minutes.
`MISSING_SCOPE`	This call needs a scope the key doesn’t have, such as `databases:read` for the metrics of a database.	Use a key with that scope.
`RESOURCE_NOT_ALLOWED`	The key is restricted to other applications and databases, or none it covers matches that name.	Use a key that covers the resource.
`TOOL_RATE_LIMITED`	A limit was reached.	Wait for the time in the summary.
`TOOL_EXECUTION_FAILED`	The same tool hit a limit twice in a row, or it failed.	Wait a few minutes or use the dashboard.
`APP_NOT_FOUND`, `DATABASE_NOT_FOUND`	No application or database matches the name or ID.	Ask the client to list them first.

A tool your key can’t use, or one that doesn’t exist, answers the JSON-RPC error -32602 Unknown tool. Check the key’s scopes. Other codes come from the tool itself, and the summary explains them.

​Limits

​TOOL_RATE_LIMITED

​Errors

​HTTP errors

​While connecting

​Tool results