> ## Documentation Index
> Fetch the complete documentation index at: https://docs.metaphi.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Overview

> Harwell is a hosted z/OS-compatible runtime that compiles and runs COBOL, JCL, CICS and Db2 code from any MCP client.

Harwell compiles and runs mainframe estate code on a hosted runtime you call over MCP: you send the code, and Harwell returns what a mainframe would have shown you.

* **Batch.** Submit JCL jobs: steps, DD statements, return codes, SORT and the common utilities, cataloged procedures, and chains of jobs with dependencies and one clock.
* **Online.** Start CICS transactions from the PCT. Screens are typed one attention key at a time, BMS mapsets are assembled from their macro source, and the COMMAREA carries state from task to task.
* **Db2.** Run `EXEC SQL` in batch and online programs, including SQL in CALLed subprograms. Query the tables afterwards with read-only SQL.
* **Data sets.** Sequential, fixed and variable record formats, VSAM KSDS and RRDS, GDGs. List a run's catalog and read records raw or through a copybook.
* **Codebases in place.** Run a whole estate by its repository, ref and path, or by a tree you send. Programs, copybooks and procedures are found through the search order the codebase declares.
* **Terminals.** Open a browser 3270-style screen for a person to drive a transaction by hand, then read back what they pressed.
* **Systems.** Keep a named mainframe state across calls, with its data sets, tables and queues. Checkpoint it and restore it.

Every result opens with a one-line verdict, then the compiler listing, the job log or the screens, and links to the full report, every listing and every spool file.

## Endpoint

```
https://harwell.metaphi.ai/mcp/
```

A streamable HTTP MCP server. See [Connect an MCP server](https://docs.metaphi.ai/account/mcp.md).

## Next

* [Quickstart](https://docs.metaphi.ai/harwell/quickstart.md): compile and run a COBOL job in a few minutes.
* [Concepts](https://docs.metaphi.ai/harwell/concepts.md): mainframe terms mapped to what you know from distributed systems.
* [Tools](https://docs.metaphi.ai/harwell/tools.md): every tool, its parameters and the scope it needs.


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