POSTFACT — Resolve Ambiguous Side Effects Before Retry

Resolve whether an uncertain side-effecting action completed before software retries it.

Quick Install

Automated & IDE Setup

Copy the AI prompt to install this server into Claude Code, Cursor, or another agent — or use 1-click editor setup below.

Add to Cursor Add to VS Code

Manual Client & Custom JSON ConfigExpand JSON ▾

Client Config & Setup

Choose your client or environment

Target File:~/Library/Application Support/Claude/claude_desktop_config.json

claude_desktop_config.json

{
  "mcpServers": {
    "postfact-resolve-ambiguous-side-effects-before-retry": {
      "command": "npx",
      "args": [
        "-y",
        "postfact-resolve-ambiguous-side-effects-before-retry"
      ]
    }
  }
}

💡 Paste the JSON block into your client's configuration file under mcpServers, then restart the application.

Documentation Overview

POSTFACT

Did the call actually happen?

POSTFACT is a tiny ambiguous-outcome resolver for autonomous software. Use it after a side-effecting API/tool action fails ambiguously and before retrying.

Production: https://postfact-api-production.up.railway.app

It is intentionally strict:

DONE only when affirmative evidence establishes completion.
NOT_DONE only when affirmative evidence establishes non-execution.
UNKNOWN whenever evidence is insufficient. UNKNOWN is the safe default.

POSTFACT does not execute the underlying action, move money, or pretend a timeout means failure.

REST

Production endpoint: POST https://postfact-api-production.up.railway.app/v1/resolve

Input accepts method/status/failure, side-effect and idempotency context, durable references, and optional affirmative evidence. Output is state, retry_safe, confidence, evidence, and next.

MCP

Remote endpoint: POST https://postfact-api-production.up.railway.app/mcp

Tool: resolve_outcome

The tool description explicitly tells agents to invoke POSTFACT after an ambiguous side-effect failure and before retry.

Middleware-shaped contract

server.ts

const outcome = await postfact.resolve(failureContext)
if (outcome.state === 'DONE') return completed
if (outcome.state === 'NOT_DONE' && outcome.retry_safe) return retry()
return verifyOrHold()

Future SDKs can wrap retry middleware without changing the wire contract.

POSTFACT + RECOVER

POSTFACT answers what can we establish happened? RECOVER answers what is the safest next action? A future retry stack can call POSTFACT first, then RECOVER when the outcome remains uncertain.

Safe discovery and demo

Health: GET https://postfact-api-production.up.railway.app/health
Demo: GET https://postfact-api-production.up.railway.app/demo
Activity: GET https://postfact-api-production.up.railway.app/activity
Machine-readable activity: GET https://postfact-api-production.up.railway.app/activity.json

GET /demo is deliberately excluded from real-use analytics.

Real-use scoreboard

GET /activity shows the permanent FIRST 10 TRUE STRANGERS scoreboard. GET /activity.json exposes its machine-readable summary. Demo/internal traffic is excluded. Production persistent storage is mounted at /data.

Run

Terminal

npm test
npm start

Default port: 8080.

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Frequently Asked Questions about POSTFACT — Resolve Ambiguous Side Effects Before Retry

Add the following block to your claude_desktop_config.json under mcpServers: "mcpServers": { "postfact-resolve-ambiguous-side-effects-before-retry": { "command": "npx", "args": ["-y", "POSTFACT — Resolve Ambiguous Side Effects Before Retry"] } }

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Technical Specs & Signals

CategoryDeveloper Tools

27Quality signal: Emerging · 27/100How this signal is calculated ▾

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{ "mcpServers": { "postfact-resolve-ambiguous-side-effects-before-retry": { "command": "npx", "args": [ "-y", "postfact-resolve-ambiguous-side-effects-before-retry" ] } } }