Routing Number Bank Lookup API MCP Guide

You need to validate U.S. bank routing numbers, auto-fill bank details in a payments form, and block bad entries before they hit your ACH file. By the end of this guide, you’ll query a routing number, confirm it’s valid, and retrieve the bank’s official name, address, phone, status, and last update date using the Routing Number Bank Lookup API on Zyla API Hub—plus see how to call it from an MCP-compatible AI agent.

What this API does and when to use it

The Routing Number Bank Lookup API returns authoritative details for a U.S. bank routing number. You can validate a routing number and fetch the institution’s name, address, contact phone, branch type, active status, and last update date. It’s useful for:

ACH and bank transfer onboarding: confirm the routing number before storing or submitting a payment.
Form auto-complete: reduce typing errors by auto-filling bank name and address.
Fraud and risk checks: quickly detect typos or invalid routing numbers.
Back-office reconciliation: normalize bank metadata for ACH files and treasury systems.

All calls are made via Zyla API Hub with one key, one subscription model, and production-grade infrastructure. You can browse more finance APIs or others on Zyla API Hub, which hosts more than 10,000 public APIs.

Getting started on Zyla API Hub

Open the Routing Number Bank Lookup API page on Zyla. Click Subscribe or Start Free Trial when available, and you’ll receive an API key to authorize requests. Zyla uses a subscription + quota model (not pay-per-call). For your first API, you’ll typically see a 7-day trial or 50 requests to evaluate. There’s no Free Plan; check the API page for current access options and pricing.

Every request below uses the same auth header: Authorization: Bearer YOUR_API_KEY. Replace YOUR_API_KEY with the key from your Zyla dashboard.

Endpoints you can ship today

1) Get Bank Information

Returns detailed information for a routing number, including bank name, ACH type, address, phone, active status, and last update date.

Method: GET
URL: https://zylalabs.com/api/331/routing-number-bank-lookup-api/266/get-bank-information
Required query params:
- routingnumber (number): e.g., 121000245
- paymentType (string): e.g., ach

cURL example (copy/paste):

curl -s -X GET "https://zylalabs.com/api/331/routing-number-bank-lookup-api/266/get-bank-information?routingnumber=121000245&paymentType=ach" \
-H "Authorization: Bearer YOUR_API_KEY"

Sample JSON response:

{
"status": "success",
"data": {
"routingNumber": "121000245",
"paymentType": "ach",
"name": "Wells Fargo Bank, Na",
"addressFull": "255 2nd Ave South, Minneapolis, MN 55479",
"street": "255 2nd Ave South",
"city": "Minneapolis",
"state": "MN",
"zip": "55479",
"type": "Main Office",
"phone": "800-245-2426",
"active": true,
"lastUpdated": "2026-07-29"
}
}

What you’ll commonly use:

data.routingNumber: Echo of the queried routing number.
data.name: Official institution name for display and storage.
data.addressFull (or street/city/state/zip): For UI auto-fill and KYC recordkeeping.
data.type: Branch type (e.g., Main Office) for internal analytics.
data.phone: User support or operator verification.
data.active: Boolean indicating if the routing number is currently active.
data.lastUpdated: ISO-like date string (YYYY-MM-DD) to gauge data recency.

2) Bank Data

Validates a routing number and returns the bank name, address, and contact details.

Method: GET
URL: https://zylalabs.com/api/331/routing-number-bank-lookup-api/1353/bank-data
Required query params:
- number (number): e.g., 304082876

cURL example (copy/paste):

curl -s -X GET "https://zylalabs.com/api/331/routing-number-bank-lookup-api/1353/bank-data?number=304082876" \
-H "Authorization: Bearer YOUR_API_KEY"

Sample JSON response:

{"status":200,"success":true,"message":"Routing Bank 304082876 is valid","data":{"routing_number":"304082876","date_of_revision":"050712","new_routing_number":null,"bank":"CENTRIS FEDERAL CREDIT UNION","address":"11825 Q STREET","city":"OMAHA","state":"NE","zip":"68137","phone":"(402) 758-6536"}}

What you’ll commonly use:

data.routing_number: The validated routing number.
message and success: Quick validation signals for UI/UX.
data.bank, data.address, data.city, data.state, data.zip: Institution information for display and storage.
data.phone: Contact number for manual verification if needed.

Python example: validate + enrich a routing number

The snippet below calls the Get Bank Information endpoint, checks active status, and prints key fields you can drop into a form or operations log.

import requests

API_KEY = "YOUR_API_KEY"
ROUTING = "121000245"
PAYMENT_TYPE = "ach"

url = "https://zylalabs.com/api/331/routing-number-bank-lookup-api/266/get-bank-information"
params = {
"routingnumber": ROUTING,
"paymentType": PAYMENT_TYPE
}
headers = {
"Authorization": f"Bearer {API_KEY}"
}

resp = requests.get(url, headers=headers, params=params, timeout=10)
resp.raise_for_status()
data = resp.json()

if data.get("status") == "success" and data.get("data"):
bank = data["data"]
print("Routing:", bank.get("routingNumber"))
print("Bank:", bank.get("name"))
print("Address:", bank.get("addressFull"))
print("City/State/Zip:", bank.get("city"), bank.get("state"), bank.get("zip"))
print("Type:", bank.get("type"))
print("Phone:", bank.get("phone"))
print("Active:", bank.get("active"))
print("Last Updated:", bank.get("lastUpdated"))
else:
print("Lookup failed or returned no data:", data)

Notes:

Authorization is sent via Bearer token in the header.
Use a short timeout to avoid hanging your checkout process.
Cache successful lookups per routing number for a few hours or a day to reduce latency in forms; the lastUpdated field helps you reason about staleness.

Practical implementation details

Normalization: The two endpoints return slightly different field names (e.g., routingNumber vs. routing_number). Normalize keys if you plan to store both.
Validation flow: For a quick yes/no, the Bank Data endpoint’s success and message fields are handy. For a richer display, use Get Bank Information.
Dates: lastUpdated is returned as a string like YYYY-MM-DD. date_of_revision is a string in the sample above; store raw and render for operators if needed.
Caching: Routing numbers change infrequently, but you should still respect lastUpdated and periodically refresh cached entries.
Error handling: Check HTTP status codes and top-level fields such as status or success before reading data.
Quotas: Zyla uses subscription + quota. For the first API you try, you’ll typically see a 7-day trial or 50 requests. There is no Free Plan; check the API page for current options.

End-to-end cURL quickstart

Copy, paste, run, and replace YOUR_API_KEY with the key from your Zyla dashboard:

curl -s -X GET "https://zylalabs.com/api/331/routing-number-bank-lookup-api/266/get-bank-information?routingnumber=121000245&paymentType=ach" \
-H "Authorization: Bearer YOUR_API_KEY"

If you need a simple validity check instead, this one returns a quick summary:

curl -s -X GET "https://zylalabs.com/api/331/routing-number-bank-lookup-api/1353/bank-data?number=304082876" \
-H "Authorization: Bearer YOUR_API_KEY"

Real-world finance use cases you can ship this week

Onboarding form auto-complete: After a user enters a routing number, call Get Bank Information to fill bank name and address instantly.
ACH file validation gate: Before generating an ACH batch, run Bank Data for each routing number; block or review any entry where success is false.
Customer support tooling: Surface phone and branch type to agents handling payment failures or verifications.
Compliance records: Store address and lastUpdated alongside the routing number to support audit trails.
Treasury integration: Normalize bank data into your vendor master to reduce rejections and returns (R03/R04 style issues often trace back to invalid or stale data).

Using this API from an MCP-compatible AI agent

You can also call the same API through Zyla’s MCP endpoint from tools like Claude Code, Cursor, Windsurf, or any MCP-compatible client. Point your client to MCP with your API key, for example: https://mcp.zylalabs.com/mcp?apikey=YOUR_API_KEY.

Typical flow inside an MCP client:

List or inspect the API using a get_api_info tool with the listing id 331.
Call the endpoint using a call_api tool:
- For detailed info: endpoint id 266 (Get Bank Information) with params routingnumber=121000245 and paymentType=ach.
- For quick validation: endpoint id 1353 (Bank Data) with param number=304082876.
Read and display the returned JSON fields (e.g., name, addressFull, phone, active, lastUpdated).

This lets you wire up automated workflows such as “When a user pastes a routing number, have the agent validate it and annotate the record with bank name and phone,” without leaving your IDE.

Operational tips

Latency: Place a short in-memory cache keyed by routing number around your API calls to keep forms snappy.
Fallback UX: If the API returns an inactive status, prompt the user to confirm or try another routing number before continuing to account number entry.
Logging: Log the lastUpdated and the endpoint used for traceability.
Security: Store your Zyla API key as a secret in your CI/CD and application config, not in client code.
Monitoring: Alert on rising invalid rates; sudden spikes may indicate upstream copying errors or malicious inputs.

Where to subscribe and get help

Subscribe on the Routing Number Bank Lookup API page. If you’re new to Zyla, create an account to get your key and start testing. You’ll find the same auth model across thousands of finance and payments listings on Zyla API Hub.

FAQ

Q: What authentication do I need?
A: Send Authorization: Bearer YOUR_API_KEY with every request to the Zyla Hub URL.

Q: Which endpoint should I use to only check validity?
A: Use Bank Data (GET /1353/bank-data?number=...). It returns success and a validation message along with bank details.

Q: How do I get the bank’s full address and phone?
A: Both endpoints return address and phone. Get Bank Information provides addressFull plus decomposed street/city/state/zip and lastUpdated.

Q: Is there a free tier?
A: There is no Free Plan. For your first API, you typically get a 7-day trial or 50 requests to evaluate. Check the API page for current options and pricing.

Q: Can I call this from an AI agent?
A: Yes. Use the MCP endpoint at https://mcp.zylalabs.com/mcp?apikey=YOUR_API_KEY. Inspect listing id 331 and call endpoint 266 or 1353 with the required parameters.

Ready to implement routing number validation and bank enrichment? Create your account, grab an API key, and ship your integration: Register.