Resolve spec notation like [[Prototype]] (internal slot), %Object.prototype% (well-known intrinsic), or ~number~ (sigil enum): return clauses that mention or define it, ranked by occurrence with a bump for definition-y sections.
Part of the Tc39 server.
Free to start. No card required.
AI agents use spec.symbol_resolve to create or modify resources in Tc39. 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 spec.symbol_resolve 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 Tc39.
Write tools can modify data. A rate limit prevents runaway bulk operations from AI agents.
{
"version": "1",
"default": "deny",
"tools": {
"spec.symbol_resolve": {
"limits": [
{
"counter": "spec.symbol_resolve_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}See the full Tc39 policy for all 17 tools.
These attack patterns abuse exactly the kind of access spec.symbol_resolve gives an agent. Each links to the full case and the policy that stops it:
Other write tools across the catalogue. The same approach applies to each: rate-limit and validate the arguments.
Resolve spec notation like [[Prototype]] (internal slot), %Object.prototype% (well-known intrinsic), or ~number~ (sigil enum): return clauses that mention or define it, ranked by occurrence with a bump for definition-y sections.. It is categorised as a Write tool in the Tc39 MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Tc39 MCP server in PolicyLayer and add a rule for spec.symbol_resolve: 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 Tc39. Nothing to install.
spec.symbol_resolve 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 spec.symbol_resolve 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 spec.symbol_resolve. 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.
spec.symbol_resolve is provided by the Tc39 MCP server (tc39-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 17 Tc39 tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
4,600+ MCP servers and 31,000+ tools scanned and risk-classified.