# pk-half-life

`station__pharmacokinetics__pk-half-life` · external (needs EXECUTION_BACKEND_URL configured) · domain `pharmacokinetics` · pv-relevance `pv-core`

Calculate elimination half-life from clearance and Vd. t½ = (0.693 × Vd) / CL. Clinically: ~4–5 half-lives to reach steady state or eliminate drug.

> **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

- `clearance` *number* (required) — Systemic clearance (L/h)
- `volume_distribution` *number* (required) — Volume of distribution (L)

## Example call

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

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "station__pharmacokinetics__pk-half-life",
    "arguments": {
      "clearance": 0,
      "volume_distribution": 0
    }
  }
}
```

## Related

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