AI agents use fill_form to create or update resources in Yandex Browser MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Yandex Browser MCP Server environment.
This tool creates or modifies data reversibly by populating form fields. While it interacts with a browser and could potentially submit forms, the tool itself is scoped to filling form fields with data, which is a Write operation. It does not delete data (Destructive), move money (Financial), or execute arbitrary code (Execute) — though the broader server context includes Execute capabilities via 'evaluate'.
From the tool's definition Tool name 'fill_form' and description 'Заполнить форму данными' (Fill form with data) indicate modification of form data.
Documented attack patterns abuse exactly the kind of access fill_form gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Yandex Browser MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for fill_form:
{
"version": "1",
"default": "deny",
"tools": {
"fill_form": {
"limits": [
{
"counter": "fill_form_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}fill_form 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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Заполнить форму данными. It is categorised as a Write tool in the Yandex Browser MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Yandex Browser MCP Server MCP server in PolicyLayer and add a rule for fill_form: 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 Yandex Browser MCP Server. Nothing to install.
fill_form 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_form 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_form. 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_form is provided by the Yandex Browser MCP Server MCP server (t1trit/yandex-browser-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Yandex Browser MCP Server, 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.
18 Yandex Browser MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.