# find-cocrystal

`station__rcsb-org__find-cocrystal` · external (needs EXECUTION_BACKEND_URL configured) · domain `rcsb-org` · pv-relevance `pv-adjacent`

Find PDB entries containing a given small-molecule ligand (by name or 3-letter chem component code). Use this to discover receptor/ligand cocrystals for mechanism-of-action visualization.

> **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

- `ligand` *string* (required) — Ligand name (e.g., 'caffeine') or 3-letter chem component ID (e.g., 'CFF')
- `limit` *integer* — Maximum entries to return (default 10, max 25)

## Example call

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

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "station__rcsb-org__find-cocrystal",
    "arguments": {
      "ligand": ""
    }
  }
}
```

## Related

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