Developer Tools · Integration
OpenLegacy
Add OpenLegacy to your product for your customers, and give your AI agents governed access to it.
Embed an OpenLegacy integration so your product can reach the business logic and data still running on a customer's mainframe without anyone writing mainframe code. OpenLegacy generates APIs over legacy assets such as CICS and COBOL programs and IBM i (AS/400) programs, and its Hub is where those generated services, their extracted metadata and their deployments are managed. Each customer supplies their own Hub URL, API key and profile, so calls run against their environment under their credentials and never cross tenants. fastn owns the credential storage, retries, rate limits and API upkeep, and the same governed connection is what your AI agents use.
In your product
Embedded for your customers. Per-tenant auth, no per-customer code, maintained by fastn.
Let each customer connect their own OpenLegacy Hub so your product can call the services generated over their legacy systems with no per-customer code.
Read the metadata OpenLegacy extracted from a program so your product knows the fields an operation actually takes.
Invoke a legacy transaction from your product with the customer's own credentials rather than a shared service account.
Support customers whose legacy estates differ, program by program, as per-tenant configuration.
For your AI agents
Governed, audited access for the agents you build, through the MCP server.
An agent calls a read-only legacy service to ground an answer in the customer's own system of record, with each call logged.
An agent inspects the metadata for a program before deciding which operation to invoke.
An agent runs an approved legacy transaction within scoped permissions, with the action attributed to the tenant that authorised it.
Example prompt
Look up this account in the mainframe service and tell me the balance and status it returns.
Set up OpenLegacy in 4 steps
- 01Enable the OpenLegacy connector in your fastn dashboard.
- 02Have each customer supply their own OpenLegacy Hub URL, API key and profile.
- 03Choose which generated services your product calls and map their input and output fields, per customer.
- 04Call them from your product and expose the same connection to your agents through the MCP gateway.
Why teams use the OpenLegacy integration
What you get by embedding it with fastn instead of building it yourself.
- Ship an OpenLegacy integration without building it. Your customers connect their own OpenLegacy account inside your product and work their services, builds and deployments there, with no per-customer code on your side.
- Handle the part that actually costs time: these systems emit a lot of webhooks, and replay after downtime has to be handled. fastn owns the auth, token refresh, rate limits, pagination and breaking-change fixes, so an OpenLegacy update is not your on-call problem.
- One integration serves your product and your agents. The same governed OpenLegacy connection powers in-product features and gives AI agents scoped, audited access, so you connect engineering activity to the rest of the business without wiring it twice.
Used by these teams
Compare with
Works well with
IBM Db2
SAPOften used alongside
Tools the same teams tend to run next to OpenLegacy, across other categories.
Slack
Snowflake
Airtable
PostgreSQLOpenLegacy integration FAQ
How do I add an OpenLegacy integration to my product?
Enable the OpenLegacy connector in your fastn dashboard, then let each customer authenticate their own OpenLegacy account. fastn handles the OAuth flow, token storage and refresh per tenant, so there is no OpenLegacy client code in your app and no per-customer branch in your codebase. Setup is 4 steps.
Do my customers each connect their own OpenLegacy account?
Yes. Every connection is scoped to the individual customer, so each authorises their own OpenLegacy account and only ever sees their own services, builds and deployments. That per-tenant isolation is the point of an embedded integration: you support the long tail of customer setups without maintaining an integration per customer.
Can AI agents use this OpenLegacy integration?
Yes. The same connection is exposed to your agents through the fastn MCP gateway, with permissions scoped per tenant and every call audited. An agent calls a read-only legacy service to ground an answer in the customer's own system of record, with each call logged.
Who maintains the OpenLegacy integration?
fastn does. When OpenLegacy changes an endpoint, deprecates a field or alters its auth, the fix lands in the connector rather than in your backlog, and your customers' connections keep working.
Can I react to OpenLegacy events in real time?
Yes, through event triggers. Events are delivered per tenant and can be replayed after an outage, so a webhook missed during downtime is not silently lost.
Can an agent open or update items in OpenLegacy?
Yes, within scoped permissions, and every action is audited so an agent's changes are attributable.
What can I build with the OpenLegacy integration?
A common starting point: let each customer connect their own OpenLegacy Hub so your product can call the services generated over their legacy systems with no per-customer code. Teams also use it for the other use cases listed above, and expose it to agents for governed reads and writes.
How much does the OpenLegacy integration cost?
It is included. Pricing is based on connected accounts, not on how many connectors you enable, so adding OpenLegacy does not change your per-connector cost. You can start free with 3 connected accounts.
Add OpenLegacy to your product
Start free with 3 connected accounts. No sales call required, and no per-customer integration code.