Low Risk

get_momentum_index

Use this when an agent needs Persimmon's deterministic momentum score for a specific brand or the top of the index. Returns composite score plus four dimensions (Draw, Surge, Wedge, Hold), tier band, signal count, and last-updated timestamp. Pure read; no LLM calls in scoring.

Part of the Persimmon server.

get_momentum_index is read-only, but an agent in a loop can still rack up calls and cost. PolicyLayer caps every call before it runs. Live in minutes.

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AI agents call get_momentum_index to retrieve information from Persimmon 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 get_momentum_index 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.

policy.json
{
  "version": "1",
  "default": "deny",
  "tools": {
    "get_momentum_index": {}
  }
}

See the full Persimmon policy for all 3 tools.

Get this rule live on your own Persimmon server in minutes. PolicyLayer enforces it on every call, before it runs.

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These attack patterns abuse exactly the kind of access get_momentum_index gives an agent. Each links to the full case and the policy that stops it:

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Every attack above starts with a tool call. PolicyLayer checks each one against your policy first, so get_momentum_index only ever does what you allow.

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Other read tools across the catalogue. The same approach applies to each: allow, with a rate cap to control cost.

What does the get_momentum_index tool do? +

Use this when an agent needs Persimmon's deterministic momentum score for a specific brand or the top of the index. Returns composite score plus four dimensions (Draw, Surge, Wedge, Hold), tier band, signal count, and last-updated timestamp. Pure read; no LLM calls in scoring.. It is categorised as a Read tool in the Persimmon MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on get_momentum_index? +

Register the Persimmon MCP server in PolicyLayer and add a rule for get_momentum_index: 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 Persimmon. Nothing to install.

What risk level is get_momentum_index? +

get_momentum_index is a Read tool with low risk. Read-only tools are generally safe to allow by default.

Can I rate-limit get_momentum_index? +

Yes. Add a rate_limit block to the get_momentum_index 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.

How do I block get_momentum_index completely? +

Set action: deny in the PolicyLayer policy for get_momentum_index. 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.

What MCP server provides get_momentum_index? +

get_momentum_index is provided by the Persimmon MCP server (https://mcp.persimmonhq.com/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Persimmon tool call.

Deterministic rules across all 3 Persimmon tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.

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