TypeSafe MCP server

Ask TypeSafe's Jev for typed, calibrated judgments from your AI assistant: how likely a yes/no statement is to hold, which of your options fits, or where something sits on your own scale. Put the same questions to one state or to up to 1000 rows at once, so the assistant can triage postings, transactions or emails without reading each one. Every tool is a read: nothing changes anywhere, and no tool is money.

You need a TypeSafe account and an API key from its console. Calls are billed by input tokens, a fraction of a cent each, and Jev answers in about half a second.

#What you can ask

• "Go through the 300 postings in postings.jsonl and list the remote senior roles, with how sure Jev is of each."
• "Is this support email urgent, and which team should take it: billing, technical or sales?"
• "Sort last month's 600 card transactions into groceries, transport, software or other, and count each."
• "Rate these 40 reviews on how likely the customer is to leave, and show me the ten most at risk."
• "Which of these passages answer 'how do I reset my password'? Flag the ones Jev is unsure about for me to read."

#Install

Install in VS Code Install in Cursor Download for Claude Desktop

With Claude Code:

claude mcp add typesafe -e TYPESAFE_API_KEY_FILE="<path to API key file>" -- npx -y @foreverworks/mcp-typesafe

Claude Desktop (Settings, Developer, Edit Config) and most other clients read the same command as JSON:

{
  "mcpServers": {
    "typesafe": {
      "command": "npx",
      "args": ["-y", "@foreverworks/mcp-typesafe"],
      "env": {
        "TYPESAFE_API_KEY_FILE": "<path to API key file>"
      }
    }
  }
}

Each runs the published package on Node 22.19 or newer. VS Code and the Claude Desktop bundle ask for TYPESAFE_API_KEY_FILE as they add the server. Cursor reads it from your environment instead (${env:TYPESAFE_API_KEY_FILE}), so set it before you start Cursor. Configuration says what it holds.

#From a clone

git clone https://github.com/foreverworks/mcps.git && cd mcps
npm ci && npm run build
claude mcp add typesafe -e TYPESAFE_API_KEY_FILE="<path to API key file>" -- node "$PWD/servers/typesafe/dist/index.js"

In a JSON configuration, the command is node and its one argument the full path of servers/typesafe/dist/index.js. To share one running copy between several clients over HTTP, see docs/deploying.md.

#Configuration

Without a key the server still starts and lists its tools, and each call answers a config error naming the variable. ask_batch reads an items_file from MCP_FILE_ROOTS; that and the other variables every server shares are in docs/configuration.md.

#Getting an API key

1. Sign in at https://console.typesafe.ai and open Keys.
2. Create a key and write it to a file only you (or the server's user) can read.
3. Point TYPESAFE_API_KEY_FILE at that file.

Give each deployment its own key, so you can revoke one alone and tell them apart on the console's usage page. Only a key from TypeSafe's own console works; a reseller's key works only through the reseller's gateway.

#First run

Ask your assistant to run TypeSafe's health check. It answers with the API it talks to, the default model, and the models your key reaches. A missing key shows up here as config, a refused one as auth, before any batch starts.

#Tools

read changes nothing; every tool here is a read (billing by input tokens is metering, not a payment).

A question is a noul (the probability that a yes/no statement holds), a choice (one of 2 to 255 options, with a probability for each) or a score (the state placed on 2 to 10 levels you order from lowest to highest).

#Troubleshooting

config. No key: set TYPESAFE_API_KEY_FILE to a file holding a key from console.typesafe.ai/keys, or TYPESAFE_API_KEY for a local run.

auth. TypeSafe refused the key. Check it still exists at console.typesafe.ai/keys, and replace the file if it was revoked.

input. The question cannot be answered as asked; the message names the field (a choice needs at least two options, a score 2 to 10 levels). Above 20 rows, every row needs an id.

rate_limited. TypeSafe is still throttling or overloaded after the server's own retries. Wait a minute, or send the batch with a lower concurrency.

api. Any other refusal, a 5xx that outlived its retries, or no connection (status 0). Retry once; if it persists, run health and read the server's log.

drift. TypeSafe answered in a shape this server does not know (its SDK's types may have moved on). Please report it.

#How it works

The network. An evaluation has no side effect, so every request (POST /v1/systemone, GET /v1/models) may repeat: a 5xx or a dropped connection is tried again, and a 429 or 529 ("overloaded") waits as a rate limit, as TypeSafe's SDK does. A call times out after a minute. Every answer is checked against the SDK's types (@typesafe-ai/sdk, types only, in src/domain/schema.ts).

Batches. A batch goes on past a failed row and reports it, but stops at a failure that would fail every row (no key, a refused key), so a thousand rows do not each earn a 401. Answers join their rows by id, required above 20 rows: a position is only safe to join on while you can check the rows by eye.

Rows from a file. Instead of typing rows into items, pass items_file: JSONL with one {"id", "state"} object per line, or a JSON array of them, by path inside MCP_FILE_ROOTS (or as content_base64 with its sha256, from a script). The rows never pass through a model, so they cannot change on the way; a malformed row fails the call with its line number before anything is sent. The reply names the file's sha256 and size.

Verdicts. With thresholds for a question, each row's answer gets act (sure enough to act on), review (a person should look) or abstain (do not use it), from the answer's certainty: for a noul |p - 0.5| x 2 (p 0.95 and p 0.05 are both 0.9), for a choice or a score the confidence TypeSafe returns. The certainty is rounded down to three places, the number the row shows, and must be strictly above act_above to act and above review_above to be reviewed. Once thresholds are tuned, pin model to a versioned Jev: jev-latest can move under them.

Choosing rows. where lists only the answered rows meeting every condition you give per question: true or false for a noul (a yes is p >= 0.7, a no p <= 0.3, as the summary counts them), labels for a choice, min and max on the value a row shows, and verdict. top keeps the k rows with the highest p or score for one question, and counts tallies the answers of the rows where kept; the summary still covers every row. Every condition is checked before a request is sent, so a label that is not an option fails the call, not a thousand rows.

npx tsx scripts/smoke.ts drives the built server against the real API, for a few thousand input tokens: health, one ask per question type, a five-row batch saved to the outbox, and one input failure that never reaches TypeSafe.

#Limitations

• Judgments only. Jev writes no text and does no multi-step reasoning. Keep rules, lookups and arithmetic in code, and threshold the probabilities (thresholds does it per question).
• where joins conditions with "and" only. For "or", read the rows from a saved JSONL, or ask a question that states the alternatives.
• At most 1000 rows a call; split a larger set.
• A batch's reply lists every row unless list says otherwise. For a large batch, pass list: "none" or "failed" with save, and read the JSONL.

#Other servers for TypeSafe

Searched 2026-10-15. TypeSafe publishes none: its GitHub organisation has the SDKs, agent skills and an n8n node. Two community servers are on npm:

• typesafe-mcp: stdio under Bun, the key in an environment variable, batches over files matched by a glob, with an act, review or abstain verdict per answer.
• @y0usaf/typesafe-mcp: stdio, one evaluate tool.

This one exists for what neither offers: it also runs over HTTP as a service of its own, with its key in a file the calling client never reads; it saves a batch's full answers as JSONL in an outbox and names the file's SHA-256; and it follows the conventions every server in this repository shares. Its verdicts and its where, top and counts follow typesafe-mcp's, with thresholds set per question rather than per call.