jev-workbench

Local service to define, test and publish versioned Jev judgment functions, callable over HTTP by backends and over MCP by agents.

MCP serverbetaMIT

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Overview

Jev Workbench lets you write a judgment once and call it from everywhere. Judgment functions are small, versioned decisions built on Jev, such as is this ticket about billing or does this evidence support that claim. You define one in a local browser UI, preview it on real input, save test cases and publish a version; from then on the same published version answers your backend over HTTP and your coding agents over MCP.

The TypeSafe vendor key never leaves the machine. Callers receive scoped client tokens pinned to the function versions they were granted, and agents use a credential file. A keyless demo seeds a ticket_route@1 function with saved cases and a restricted client, simulating every answer with no network or charges: a refund request returns ok with department billing, an unclear input returns needs_review, and simulated errors return 502 or 504. Demo state is kept separate from production. It requires Node.js 24 and pnpm, is MIT licensed, and has English and Chinese documentation.

What the decision model decides

Type	Question	Answers
Choice	Which department is this ticket about (example ticket_route function)?	—
Yes / no	Does this evidence support that claim?	—

How it works

Define a judgment function in the browser
Preview on real input and save cases
Publish a version and grant scoped tokens
Backends call over HTTP and agents over MCP; low confidence returns needs_review

Strengths

Same versioned function for backends and agents
Vendor key stays local; scoped, version-pinned tokens
Keyless simulated demo
Explicit error codes for upstream failures

Caveats

Requires running a local service
Node.js 24 and pnpm required

Getting started

pnpm install --frozen-lockfile && pnpm build && pnpm demo, then open http://127.0.0.1:17430.

At a glance

Type: MCP server
Status: beta
Language: TypeScript
Runtime: Local service + MCP server
Has code: yes
License: MIT

Use cases and integrations

Infra / SDKs / Integrations537

How curated lists describe it

Defines, tests, and publishes Jev decision functions in a local UI so backends and Agents can call fixed versions.
logicrw/awesome-jev-projects
Build versioned judgment functions on TypeSafe's Jev once, then call the same published version from your backend over HTTP and from coding agents over MCP. The vendor key stays on your machine.
hellogumbo/awesome-jev

Frequently asked questions

What is a judgment function?

A small, versioned Jev decision such as routing a ticket, published once and callable over HTTP or MCP.

Where does the TypeSafe key live?

Only on your machine; callers get scoped tokens pinned to granted versions.

Can I try it without a key?

Yes, `pnpm demo` simulates all answers with no network or charges.

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