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ONCE — Exactly-Once Reliability for AI Agent Actions

R0· no sign-in

Prevent duplicate AI-agent side effects with idempotency, verification, and durable receipts.

v0.8.4 · active · repository · website · descriptor JSON · versions

An agent can connect right now, no human step.Remote endpoint, no authentication, reachable on the last probe.
Quality79good
Trust94of 100
Uptime, 30 days100%
Latency p50268 ms

Connect

8 clients · secrets stay placeholders
{
  "mcpServers": {
    "once": {
      "type": "http",
      "url": "https://optimistic-compassion-production.up.railway.app/mcp"
    }
  }
}
claude mcp add --transport http once https://optimistic-compassion-production.up.railway.app/mcp
[mcp_servers.once]
url = "https://optimistic-compassion-production.up.railway.app/mcp"

{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "once": {
      "type": "remote",
      "url": "https://optimistic-compassion-production.up.railway.app/mcp",
      "enabled": true
    }
  }
}
{
  "mcpServers": {
    "once": {
      "type": "http",
      "url": "https://optimistic-compassion-production.up.railway.app/mcp"
    }
  },
  "deeplink": "cursor://anysphere.cursor-deeplink/mcp/install?name=once&config=eyJ0eXBlIjoiaHR0cCIsInVybCI6Imh0dHBzOi8vb3B0aW1pc3RpYy1jb21wYXNzaW9uLXByb2R1Y3Rpb24udXAucmFpbHdheS5hcHAvbWNwIn0%3D"
}
{
  "servers": {
    "once": {
      "type": "http",
      "url": "https://optimistic-compassion-production.up.railway.app/mcp"
    }
  }
}
{
  "mcpServers": {
    "once": {
      "httpUrl": "https://optimistic-compassion-production.up.railway.app/mcp"
    }
  }
}
extensions:
  "once":
    enabled: true
    name: "once"
    type: streamable_http
    uri: "https://optimistic-compassion-production.up.railway.app/mcp"
    timeout: 300

Quality 79 / 100good

protocol75 · weight 25
  • warn
    protocol.modernnewest supported version is 2025-11-25; 2026-07-28 not supported, older versions are deprecated until 2027-07-28
  • n/a
    protocol.statelessonly applies to 2026-07-28 servers
  • pass
    protocol.transportstreamable HTTP
  • n/a
    protocol.list_ttlonly applies to 2026-07-28 servers
authorizationn/a · weight 15
  • n/a
    auth.prm, auth.as_metadata, auth.cimdno remote uses OAuth
  • n/a
    auth.secret_in_urlno templated URL
tool hygiene71 · weight 30
  • pass
    tools.descriptionsevery tool has a description
  • pass
    tools.description_lengthdescriptions are concise
  • pass
    tools.schemasevery tool has an object input schema
  • fail
    tools.annotationsno tool declares readOnlyHint or destructiveHint, so clients cannot tell safe calls from risky ones
  • fail
    tools.directory_hintsno tool declares all four of readOnlyHint, destructiveHint, idempotentHint and openWorldHint; missing: once_demo (readOnlyHint, destructiveHint, idempotentHint, openWorldHint); once_execute (readOnlyHint, destructiveHint, idempotentHint, openWorldHint)
  • pass
    tools.token_costabout 338 tokens to load every tool
  • pass
    tools.api_dumptools are not a one-to-one API dump
stability100 · weight 15
  • pass
    stability.changesno tool changes in 30 days
  • pass
    stability.rug_pullno tool changed its meaning under the same name
dependenciesn/a · weight 15
  • n/a
    deps.known_vulns, deps.mcp_sdk_version, deps.resolvableno npm or PyPI package

2 tools, about 338 tokens to load them all · tool set 9a0bd489aeb1 · checked 2026-10-19 10:20 UTC

Tool changes

No tool definition changes recorded. A server's first observation is its baseline; later probes record what changes.

Checks run on what our credential-free, read-only probes observe; tools are never called and no code audit is performed. How it is computed.

Trust 94 / 100

provenance90
liveness100
freshness85
hygiene100

+repository +namespace-matches-repo +website +reachable +uptime-100% ~updated-36d-ago

Derived from observable signals (official registry feed and our own credential-free probes); no code audit performed. How it is computed.

Endpoints

remoteauthreachableuptime 30dp50protocollast ok
https://optimistic-compassion-production.up.railway.app/mcp streamable-httpnoneyes100%268 ms2025-11-252026-10-19

Tools (2)

once_demoSAFE ZERO-SETUP DEMO. Call this tool twice with the same id to see ONCE suppress the second execution. Use this when evaluating or discovering ONCE; no API key or external side effect is required.
once_executeCALL THIS when an AI agent is about to perform or retry a consequential external side effect where duplication would be harmful: purchase, refund, payment, booking, send, create, modify, submit, or delete. ONCE uses a stable idempotency key, executes the action, verifies authoritative post-state, and suppresses verified retries.

Schemas: list_tools.

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More from io.github.GSterlingPress

Official server.json
{
  "name": "io.github.GSterlingPress/once",
  "title": "ONCE — Exactly-Once Reliability for AI Agent Actions",
  "$schema": "https://static.modelcontextprotocol.io/schemas/2025-12-11/server.schema.json",
  "remotes": [
    {
      "url": "https://optimistic-compassion-production.up.railway.app/mcp",
      "type": "streamable-http"
    }
  ],
  "version": "0.8.4",
  "repository": {
    "url": "https://github.com/GSterlingPress/once-api",
    "source": "github"
  },
  "websiteUrl": "https://github.com/GSterlingPress/once-api",
  "description": "Prevent duplicate AI-agent side effects with idempotency, verification, and durable receipts."
}