Lightweight single-purpose color derivation. Derive accessible background scales, text colors, brand color 4-token sets, status color variants, or light↔dark counterpart backgrounds. Returns raw tokens as JSON — no CSS wrapping. Use this when you need a quick answer like 'give me accessible grays...
Part of the Tokven server.
Free to start. No card required.
AI agents call derive_color to retrieve information from Tokven without modifying any data. This is common in research, monitoring, and reporting workflows where the agent needs context before taking action. Because read operations don't change state, they are generally safe to allow without restrictions -- but you may still want rate limits to control API costs.
Even though derive_color only reads data, uncontrolled read access can leak sensitive information or rack up API costs. An agent caught in a retry loop could make thousands of calls per minute. A rate limit gives you a safety net without blocking legitimate use.
Read-only tools are safe to allow by default. No rate limit needed unless you want to control costs.
{
"version": "1",
"default": "deny",
"tools": {
"derive_color": {}
}
}See the full Tokven policy for all 5 tools.
These attack patterns abuse exactly the kind of access derive_color gives an agent. Each links to the full case and the policy that stops it:
Other read tools across the catalogue. The same approach applies to each: allow, with a rate cap to control cost.
Lightweight single-purpose color derivation. Derive accessible background scales, text colors, brand color 4-token sets, status color variants, or light↔dark counterpart backgrounds. Returns raw tokens as JSON — no CSS wrapping. Use this when you need a quick answer like 'give me accessible grays for this background' or 'what text colors work on #0d0d0d?'. It is categorised as a Read tool in the Tokven MCP Server, which means it retrieves data without modifying state.
Register the Tokven MCP server in PolicyLayer and add a rule for derive_color: 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 Tokven. Nothing to install.
derive_color is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the derive_color 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 derive_color. 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.
derive_color is provided by the Tokven MCP server (tokven-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 5 Tokven tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
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