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POSTFACT — Resolve Ambiguous Side Effects Before Retry

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

Source code Website Documentation

Install

Add this to your client's MCP configuration (Claude Desktop: claude_desktop_config.json; Cursor: .cursor/mcp.json; VS Code and others use the same "mcpServers" shape).

Remote (streamable-http)
Claude Code 
claude mcp add --transport http postfact-resolve-ambiguous-side-effects- 'https://postfact-api-production.up.railway.app/mcp'
JSON configuration (Claude Desktop, Cursor, VS Code) 
{
    "mcpServers": {
        "postfact-resolve-ambiguous-side-effects-": {
            "type": "http",
            "url": "https://postfact-api-production.up.railway.app/mcp"
        }
    }
}

Documentation

From the project's README on GitHub, refreshed weekly. Links open on GitHub.

Contents
  1. POSTFACT
  2. REST
  3. MCP
  4. Middleware-shaped contract
  5. POSTFACT + RECOVER
  6. Safe discovery and demo
  7. Real-use scoreboard
  8. Run

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

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

npm test
npm start

Default port: 8080.

Frequently asked questions

What is POSTFACT — Resolve Ambiguous Side Effects Before Retry?

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

How do I install POSTFACT — Resolve Ambiguous Side Effects Before Retry?

It runs as a remote server. In Claude Code: claude mcp add --transport http postfact-resolve-ambiguous-side-effects- 'https://postfact-api-production.up.railway.app/mcp'. For other clients, paste the JSON configuration from this page into their MCP settings.

Does POSTFACT — Resolve Ambiguous Side Effects Before Retry need an API key?

Its registry entry lists no required key or secret. Some features may still need an account with the service it connects to.

Is POSTFACT — Resolve Ambiguous Side Effects Before Retry open source?

Its code is public on GitHub, but the repository does not declare a standard license.

Who maintains POSTFACT — Resolve Ambiguous Side Effects Before Retry?

It is published by GSterlingPress. AI.tn lists it but does not maintain or endorse it.

From the official MCP Registry. Listing is not an endorsement: review a server's code and permissions before giving it access to your data.