When using this tool, always use the `jq_filter` parameter to reduce the response size and improve performance. Only omit if you're sure you don't need the data. Returns a list of signing keys. # Response Schema ```json { type: 'object', properties: { data: { type: 'array', ...
Part of the Mux MCP server. Enforce policies on this tool with Intercept, the open-source MCP proxy.
AI agents call list_system_signing_keys to retrieve information from Mux 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 list_system_signing_keys 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.
tools:
list_system_signing_keys:
rules:
- action: allowSee the full Mux policy for all 98 tools.
Agents calling read-class tools like list_system_signing_keys have been implicated in these attack patterns. Read the full case and prevention policy for each:
Other tools in the Read risk category across the catalogue. The same policy patterns (rate-limit, allow) apply to each.
When using this tool, always use the `jq_filter` parameter to reduce the response size and improve performance. Only omit if you're sure you don't need the data. Returns a list of signing keys. # Response Schema ```json { type: 'object', properties: { data: { type: 'array', items: { $ref: '#/$defs/signing_key' } } }, required: [ 'data' ], $defs: { signing_key: { type: 'object', properties: { id: { type: 'string', description: 'Unique identifier for the Signing Key.' }, created_at: { type: 'string', description: 'Time at which the object was created. Measured in seconds since the Unix epoch.' }, private_key: { type: 'string', description: 'A Base64 encoded private key that can be used with the RS256 algorithm when creating a [JWT](https://jwt.io/). **Note that this value is only returned once when creating a URL signing key.**' } }, required: [ 'id', 'created_at' ] } } } ```. It is categorised as a Read tool in the Mux MCP Server, which means it retrieves data without modifying state.
Add a rule in your Intercept YAML policy under the tools section for list_system_signing_keys. You can allow, deny, rate-limit, or validate arguments. Then run Intercept as a proxy in front of the Mux MCP server.
list_system_signing_keys 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 list_system_signing_keys rule in your Intercept 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 Intercept policy for list_system_signing_keys. 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.
list_system_signing_keys is provided by the Mux MCP server (@mux/mcp). Intercept sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Open source. One binary. Zero dependencies.
npx -y @policylayer/intercept