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Excalibur MCP server

online · 100% uptime
by lonniev·io.github.lonniev/excalibur-mcp·v0.43.0·3 stars
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FastMCP server for posting formatted content to X (Twitter) — Tollbooth-monetized, DPYC-native

A97/100grade A
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Safety scan
A97/100

full report

Adoption
Growing

3 stars

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If you have run it, two minutes of your experience saves the next person an afternoon.

Excalibur tools

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Public scan report

scanner v0.1.10 · 2026-10-30 · same rubric, same numbers if you re-run it

no findings
  • –Code scanremote-only server, no package to scann/a
  • Live reliabilityremote reachable in 472ms (auth required)20/20
  • –Tool poisoningtools not inspected (endpoint requires auth); not countedn/a
  • Auth qualityOAuth resource metadata advertised on 40115/15
  • Maintenancelast push 0 days ago15/15
  • Maintainer identityregistry namespace matches repository owner; GitHub account older than a year8/10
Overall 97/100. Components that don't apply are left out of the denominator. Any critical finding is an F.RubricAppeal a findingJSON

How Excalibur compares

Against every graded MCP server, from our own scans and uptime checks. Updated after each scan run.

Safety score
97/100
higher than 98% of 48,255 servers
Uptime
100%
of our recent checks; the typical remote server answers 100%
Response time
419 ms
faster than 35% of 30,031 servers
GitHub stars
3
more than 80% of 28,688 servers

Release history: 2 versions in the registry since 2026-08-29, latest 2026-10-21, typically one every 53 days.

Install Excalibur in Claude Code, Cursor or VS Code

claude mcp add --transport http excalibur-mcp https://excalibur-mcp.fastmcp.app/mcp
Add to Cursor

What the publisher says

From the Excalibur repository's README, as published. We do not edit it. Read it on GitHub

eXcalibur MCP

Sword-swift posting of pretty tweets to X (Twitter) via AI agents, monetized with Bitcoin Lightning micropayments through the DPYC(TM) Tollbooth protocol.

eXcalibur is a FastMCP server that lets AI agents post to X (Twitter) with rich Unicode formatting and optional images. Patron authentication for X uses OAuth2 Authorization Code + PKCE -- no credentials appear in chat. Operator credentials (X app keys, BTCPay) arrive via human-in-the-loop Secure Courier and are stored in the operator's per-operator Neon vault schema. Tool calls are metered with Tollbooth DPYC(TM) pre-funded Lightning balances -- Don't Pester Your Customer.

Part of the DPYC(TM) Social Contract.

Getting Started

Connect via Horizon -- no local install needed:

https://www.fastmcp.cloud/mcp/lonniev/excalibur-mcp

Step 1: Check Session

Call excalibursessionstatus to see your current session state. If you have an active session with funded credits, you are ready to post.

Step 2: X OAuth2 + PKCE (Patron Credentials for X)

Nostr client.

  1. Get your Nostr npub -- use the dpyc-oracle's howtojoin() tool, or any

Open the primary authorize_url (not a shortlink) in your browser and authorize the app on X.

  1. Call excaliburbeginoauth(npub=) -- returns an authorize_url.

exchange, vaults the tokens, and activates your session.

  1. Call excaliburcheckoauth_status(npub=) -- completes the code

Sessions are keyed by npub. Tokens are stored in the Neon vault and auto-refresh on expiry.

Step 3: Secure Courier (Operator Credentials)

Operator credentials (X OAuth2 app keys, BTCPay connection) are delivered via Secure Courier (service="excalibur-operator"). This is a human-in-the-loop flow: the operator consciously approves each credential delivery via their Nostr client. On receive_credentials, the relay DM is destructively drained -- credentials exist only in the Neon vault after receipt.

Credits Model

Tool calls cost apisats per call. Credits have a tranchelifetime -- each purchase creates a tranche that expires after the configured lifetime. Auth and balance tools are always free. Use excaliburcheckbalance to see your balance and tranche expiry. Top up via excaliburpurchasecredits.

Available Tools

Standard Tools (from the wheel)

Standard DPYC(TM) tools are registered by registerstandardtools() from tollbooth-dpyc. These include session management, credit operations, Secure Courier, pricing, notarization, and Oracle delegation. Each tool is identified by a deterministic UUID v5.

Domain Tools (eXcalibur-specific)

Shortened. The full README is on GitHub.

Nothing above is checked by us. What we check is on the safety report.

Grade history

  • 2026-10-30restoreB → Ascore 97

Excalibur: common questions

Is Excalibur MCP server safe?
Yes, by our scan: it is graded A (97/100). Read the Excalibur safety report
How do I install Excalibur?
It runs remotely at excalibur-mcp.fastmcp.app. Add it to Claude Code, Cursor, VS Code or Claude Desktop with the snippets above, or call it through the mcp.market gateway without installing anything.
Does Excalibur need an API key?
No key to paste: it signs you in with OAuth when your client connects.
Is Excalibur maintained?
The last commit was 5 days ago (2026-10-29). The latest release is v0.43.0.
Is Excalibur up?
100% of our last 28 checks got an answer. We check remote servers about four times a day.
How does Excalibur compare with other MCP servers?
safety score 97/100 (higher than 98% of 48,255 servers); uptime 100% (of our recent checks; the typical remote server answers 100%); response time 419 ms (faster than 35% of 30,031 servers). Full comparison.

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