Assay
Put a policy firewall in front of MCP tool calls so solo builders can block, audit, and replay agent actions with evidence.
Overview
Assay is a MCP server for the Ship phase that firewalls MCP tool calls with block, audit, and replay backed by evidence bundles.
What is this MCP server?
- Acts as a firewall layer on MCP tool invocations—block, allow, and audit in one path
- Evidence bundles for replay and post-incident review of what the agent actually called
- stdio MCP package (mcpb) with pinned release artifact and fileSha256 in server metadata
- Pairs with Assay MCP Server proxy for fuller policy-enforcing deployments
- Version 3.1.0 published via GitHub release channel
- Server version 3.1.0 in registry metadata
- 1 stdio mcpb package with fileSha256 pin in server.json
- Transport type stdio per MCP registry schema
Community signal: 5 GitHub stars.
What problem does it solve?
Agents can invoke powerful MCP tools with little visibility, so one bad call can leak secrets or mutate production without a defensible audit trail.
Who is it for?
Indie builders connecting multiple MCP servers to coding agents who need enforcement and auditability before granting destructive tools.
Skip if: Teams that only use built-in IDE tools with no MCP layer, or anyone who wants a full SIEM instead of MCP-specific call governance.
What do I get? / Deliverables
After you register Assay, MCP tool traffic can be blocked or allowed by policy, logged, and replayed with evidence you can share in reviews or incidents.
- Policy-gated MCP tool call path
- Audit and replay capability with evidence bundles
- Pinned v3.1.0 mcpb artifact registration in your MCP config
Recommended MCP Servers
Journey fit
How it compares
MCP security proxy and evidence layer, not an agent skill that writes application code.
Common Questions / FAQ
Who is Assay for?
Solo and small-team builders who run MCP-enabled agents and want firewall-style control plus replayable evidence on every tool call.
When should I use Assay?
Use it when you are adding high-risk MCP tools (shell, DB, deploy) or preparing for security review, compliance questions, or post-mortems on agent behavior.
How do I add Assay to my agent?
Add the io.github.Rul1an/assay MCP server entry to Claude Desktop, Claude Code, or Cursor via the MCP registry package (stdio mcpb), using the release URL from the server.json identifier field.