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Once MCP server

by stringsofthemind-oss·io.github.stringsofthemind-oss/once·v0.1.2
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Execution-safety MCP for AI coding agents protecting consequential writes from unsafe retries.

B80/100grade B
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Safety scan
B80/100

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

Once tools (8, 1 write)

write = sends, deletes, buys or posts

Read from the package source without running it. The installed server may list more.

  • once_apply_protection

    Transactionally apply exactly one PATCHABLE Once protection candidate. This modifies source code and creates a backup. Call once_plan_protection first, show the proposed target to the user, and only proceed after explicit approval.

  • once_assess_project

    Use this first when code performs payments, refunds, payouts, bookings, orders, provisioning, database/API writes, consequential messaging, deployments, MCP writes, or other side effects. Scans the project for likely consequential operations without modifying files.

  • once_explain_risk

    Explain why a specific operation may need Once. Use when an agent or developer is deciding whether a payment, refund, booking, order, provisioning action, database/API mutation, webhook, deployment, MCP write, or other external side effect needs execution-safety protection.

  • once_live_proof

    Return the current demonstrated Once proof, public evidence links, and safe claim boundaries. Use when deciding whether Once has evidence for duplicate suppression rather than relying on marketing language.

  • once_plan_protection

    Review candidate operations for Once protection without applying code changes. Use after once_assess_project to understand which call sites are patchable and why.

  • once_plan_setup

    Preview how Once would be configured in a project without applying setup. Use after assessing a project and before allowing an agent to install or configure Once.

  • once_setup_project

    Apply Once setup to a project. This may install dependencies and modify project files. Call once_plan_setup first, present the plan to the user, and only call this tool after explicit approval.

  • once_verify_connectionwrite action

    Run Once Doctor to verify that ONCE_API_KEY is present, Once Cloud is reachable, the key is accepted, the truth endpoint works, and the safety probe passes. Does not print the API key.

Public scan report

scanner v0.1.9 · 2026-09-20 · same rubric, same numbers if you re-run it

no findings
  • Code scan3 source files scanned25/25
  • –Live reliabilityno gateway calls yet and no remote to proben/a
  • –Tool poisoningtools not inspected (local package is not executed); not countedn/a
  • Auth qualitystatic API keys via environment variables6/15
  • Maintenancelast push 0 days ago15/15
  • Maintainer identityregistry namespace matches repository owner6/10
Overall 80/100. Components that don't apply are left out of the denominator. Any critical finding is an F.RubricAppeal a findingJSON

Install directly

Runs npx -y @once-agent/mcp on your machine. Read the scan report first; the gateway never runs local packages.

claude mcp add once -- npx -y @once-agent/mcp
Add to Cursor

Once: common questions

Is Once MCP server safe?
Mostly: it is graded B (80/100). Read the Once safety report
How do I install Once?
It runs on your machine. Copy the Claude Code, Claude Desktop or Cursor config from the install section.
Does Once need an API key?
Yes. The registry entry asks for ONCE_API_KEY.
Is Once maintained?
The last commit was in the last day (2026-09-20). The latest release is v0.1.2.

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