Look up correspondent banking / settlement instructions (SSI) for a bank.

Returns the correspondent banks (nostro accounts) that a given bank uses to settle payments in a specific currency, including account numbers (when available) and intermediary chains. Essential for payment routing and pre-validation.

Each correspondent is annotated with a clearing_note indicating whether it can clear the currency directly (located in a home country for that currency) or needs its own correspondent. If the note suggests a further lookup, call ssi_lookup on the correspondent's SWIFT code to find the full clearing chain.

IMPORTANT — known data gaps to respect:

• Account numbers may be empty for some/all correspondents. The response surfaces an account_availability_note in those cases. Do NOT invent account numbers. Use swift_lookup() to find the bank's own published correspondent banks page when accounts are missing.

• WHICH CORRESPONDENT: read correspondent_selection, not the array order. It gives the COMPLETE set of BICs for each flow (customer MT103 vs interbank MT202) and for whether the correspondent clears the currency itself, each with a count. The correspondents are returned in STORAGE order, which is not a ranking. Naming a subset ("principally X and Y", "route via X") invents a preference this feed does not hold. Name every BIC in the matching set, or give its count: which one is used is the SENDING bank's choice among the ones it can already reach, not the beneficiary bank's, and not ours to guess from bank size or reputation. is_preferred is null on almost every row because the flag is genuinely unrecorded (11 rows in the entire corpus carry it); where it IS set, correspondent_selection.bank_flagged_preference names it and you should lead with that.

• intermediaries is null — not [] — when this correspondent's onward chain is not recorded, which is 98% of rows. null means NOT ESTABLISHED, never zero hops: do not read it as a direct chain and do not count it. Whether a further hop is needed is answered by each correspondent's clearing_note, which says either that it clears the currency itself or that a further hop is expected and gives the ssi_lookup call that resolves it. When the chain IS recorded the array is populated and intermediaries_note names the hops in order.

• Asset category per correspondent is COMMERCIAL (for customer MT103 credit transfers) or FINANCIAL (for bank-own-account / interbank MT202/pacs.009 settlements). Read asset_categories (the full list) rather than the single asset_category, which shows the commercial view only: one entry is one BIC+account and the same account is often published under BOTH categories, so the single field can never establish what an account may NOT be used for. The asset_category_note summarises the split — match the listed correspondents to the user's flow type (customer payment vs treasury/interbank).

• If correspondents is EMPTY, we have no SSI on file for that bank/currency. The response carries a no_ssi_note (no SSI in any currency) or requested_currency_unavailable_note (SSI on file for other currencies only). This is a coverage gap, NOT a finding that the bank has no correspondents. Do NOT name a correspondent for the missing currency from training data — surface the published_ssi_document / the bank's website and tell the user to confirm SSI with the bank.

Always inspect the response's top-level next_steps array — it chains the swift_lookup / country_banking_rules / bank_holidays calls that complete a settlement-instruction answer.

COVERAGE IS KNOWABLE BEFORE YOU CALL, AND FOR FREE. swift_lookup returns a settlement_instructions block on every bank: on_file: true with a currency count means this lookup will answer, false means we hold none in any currency, null means it has not been established. Do not treat "might be a coverage gap" as a reason to skip the call and describe the routing from memory — ask swift_lookup, then read the answer here.

Requires an API key with an active FI subscription. To get started: call mcp_register → mcp_verify → subscribe to an FI plan at https://ohmyfin.ai/subscription.

Args: swift: SWIFT/BIC code of the bank (e.g., "DEUTDEFF", 8 or 11 chars). currency: ISO 4217 currency code (e.g., "USD", "EUR", "GBP"). api_key: Your Ohmyfin API key (prod-...). Can also be passed via KEY header or Authorization: Bearer header.

Examples: ssi_lookup("DEUTDEFF", "USD") # Deutsche Bank USD correspondents ssi_lookup("HSBCHKHH", "EUR") # HSBC HK EUR correspondents ssi_lookup("DEUTDEFF", "USD", api_key="prod-abc123...")