Fill a form field by its label text. Finds the input/textarea associated with the label and fills it. Works with React/Vue/Angular apps. On failure, lists available field labels for debugging.
AI agents use fill_by_label to create or update resources in Macos Control — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Macos Control environment.
This tool creates or modifies data reversibly by populating form fields with values. It does not delete data (not Destructive), execute arbitrary commands (not Execute), handle financial transactions (not Financial), or merely retrieve data (not Read).
From the tool's definition Tool description states it 'fills' form fields and 'finds the input/textarea associated with the label and fills it', which are write operations that modify form state and data.
Documented attack patterns abuse exactly the kind of access fill_by_label gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Macos Control, and nothing reaches the server without passing your rules. This is the rule we recommend for fill_by_label:
{
"version": "1",
"default": "deny",
"tools": {
"fill_by_label": {
"limits": [
{
"counter": "fill_by_label_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}fill_by_label 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.
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Fill a form field by its label text. Finds the input/textarea associated with the label and fills it. Works with React/Vue/Angular apps. On failure, lists available field labels for debugging. It is categorised as a Write tool in the Macos Control MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Macos Control MCP server in PolicyLayer and add a rule for fill_by_label: 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 Macos Control. Nothing to install.
fill_by_label is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the fill_by_label 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.
Set action: deny in the PolicyLayer policy for fill_by_label. 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.
fill_by_label is provided by the Macos Control MCP server (peterhdd/macos-control-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Macos Control, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
Free to start. No card required.
22 Macos Control tools catalogued and risk-classified — across an index of 43,000+ MCP servers.