# engram-decay-score

`station__engram__engram-decay-score` · external (needs EXECUTION_BACKEND_URL configured) · domain `engram` · pv-relevance `non-pv`

Compute temporal decay score for an engram (pure computation, no store needed).

> **Note:** This tool routes through an external execution backend. If `EXECUTION_BACKEND_URL` is unset on the server, calls return JSON-RPC error `-32603 "Tool execution backend not configured"`. Tools with `backend: native` execute in-process and are always callable.

## Agent metadata

- `idempotent`: unknown
- `read_only`: unknown
- `expected_latency_ms`: unknown (not yet contract-tested)
- `cost_tokens_estimate`: unknown

## Input schema

- `access_count` *integer* (required) — Number of times accessed.
- `created_at` *string* (required) — ISO 8601 timestamp when the engram was created.
- `half_life_days` *number* — Half-life in days. Default: 14.0.
- `last_accessed` *string* (required) — ISO 8601 timestamp of last access.
- `stale_threshold` *number* — Stale threshold [0.0, 1.0]. Default: 0.1.

## Example call

```json
POST /api/mcp
Content-Type: application/json

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "station__engram__engram-decay-score",
    "arguments": {
      "access_count": 0,
      "created_at": "",
      "last_accessed": ""
    }
  }
}
```

## Related

- [/tools](/tools) — all 3062 tools
- [/tools/engram__engram-decay-score](/tools/engram__engram-decay-score) — HTML page
- [/tools/engram__engram-decay-score/json](/tools/engram__engram-decay-score/json) — JSON form (agent-friendly)
- [/api/mcp](/api/mcp) — endpoint
- [/AGENTS.md](/AGENTS.md) — agent guide