Chain Selection

REST protocol routes are chain-aware. Pass optional ?chainId= to read or prepare against a protocol chain. MCP protocol tools take optional chainId (default Base) — see MCP chain selection.

Query parameter

Use ?chainId= on protocol reads, prepares, history, discovery, approved tokens, and transaction status.

Format	Example
Decimal	?chainId=8453
CAIP-2	?chainId=eip155:8453

Omitted chainId uses DEFAULT_REST_CHAIN_ID (shipped as 8453). Unknown, malformed, or REST-disabled values return 400 with code: "VALIDATION_ERROR".

curl -s "https://api.clocktower.finance/protocol/state?chainId=8453" | jq .
curl -s "https://api.clocktower.finance/protocol/state?chainId=eip155:8453" | jq .

POST prepares take the same query parameter (not a JSON body field):

curl -s -X POST "https://api.clocktower.finance/prepare/subscribe_by_id?chainId=8453" \
  -H "Content-Type: application/json" \
  -d '{ "from": "0xYourAddress", "id": "0x..." }'

Which routes are chain-scoped

Accept ?chainId=	Not chain-scoped
Protocol state, subscriptions, accounts, approved tokens	GET /catalog (still lists chains)
Discovery, history, profiles	GET /status, /
Prepare, readiness, POST /transactions/status	Developer keys

GET /catalog is not filtered by chain. It reports the REST default as chainId and the full registry as chains[]. Passing an unsupported chainId on any REST path still returns 400 because the worker validates the query before routing.

Discover live chains

GET /catalog → chains[] is the source of truth for which chains the hosted API currently serves:

{
  "chainId": 8453,
  "chains": [
    {
      "chainId": 8453,
      "caip2": "eip155:8453",
      "name": "base",
      "rest": true,
      "mcp": true,
      "default": true
    }
  ]
}

Field	Meaning
chainId (top-level)	REST default when the client omits ?chainId=
chains[].rest	Protocol routes may target this chain
chains[].mcp	MCP tools may target this chain (list_chains / optional tool chainId)
chains[].default	This row is DEFAULT_REST_CHAIN_ID

The registry currently ships Base mainnet as the only REST-enabled chain. Additional EVM chains can be enabled without changing the request shape — keep using ?chainId= and read chains[] at runtime.

MCP

MCP protocol tools select a chain with optional chainId (default Base). That is independent of REST ?chainId= and of DEFAULT_REST_CHAIN_ID. See MCP chain selection.

Writes

Prepare responses include chainId on the payload, unsignedTransactions, gasEstimates, and gasSummary. Connect the wallet to that chain before signing, then broadcast there. Simulation and gas estimation run on the selected REST chain.

See Write endpoints and Errors.