AI agents use set_frontmatter_key to create or update resources in Ast Editor — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Ast Editor environment.
This tool creates or modifies file metadata (frontmatter key-value pairs), which is reversible data modification. It does not delete, execute code, or move money, so Write is the appropriate category. Severity is medium because frontmatter changes could affect file behavior or configuration, but they are typically reversible and limited in blast radius compared to destructive operations.
From the tool's definition Tool name 'set_frontmatter_key' indicates modification of frontmatter metadata in files. Sibling tools like 'add_field', 'add_key', 'add_method' suggest this server specializes in file modification operations. The description is empty, limiting certainty.
Documented attack patterns abuse exactly the kind of access set_frontmatter_key gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Ast Editor, and nothing reaches the server without passing your rules. This is the rule we recommend for set_frontmatter_key:
{
"version": "1",
"default": "deny",
"tools": {
"set_frontmatter_key": {
"limits": [
{
"counter": "set_frontmatter_key_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}set_frontmatter_key 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.
Free to start. No card required.
set_frontmatter_key. It is categorised as a Write tool in the Ast Editor MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Ast Editor MCP server in PolicyLayer and add a rule for set_frontmatter_key: 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 Ast Editor. Nothing to install.
set_frontmatter_key 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 set_frontmatter_key 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 set_frontmatter_key. 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.
set_frontmatter_key is provided by the Ast Editor MCP server (kambleakash0/agent-skills). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Ast Editor, 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.
59 Ast Editor tools catalogued and risk-classified — across an index of 43,000+ MCP servers.