mcp-server-mcpindex

An MCP server for finding MCP servers, plus advisory trust verdicts agent frameworks can call before invoking a tool.

A drop-in MCP server that lets your agent discover, compare, install, and pre-flight other MCP servers from inside the agent loop. Backed by mcpindex.ai - the agent-native index of the official MCP registry (live count at mcpindex.ai/stats), screened and drift-monitored daily.

Install

npm install -g mcp-server-mcpindex

This is the directory / advisory client (recommend, search, trust). It does not install the in-path drift gate — that is curl -fsSL https://mcpindex.ai/install.sh | sh.

Or connect remotely (no install)

Prefer not to install anything? mcpindex is also a hosted remote MCP server. Point any client that supports remote MCP (Claude connectors, Cursor, etc.) at:

https://mcpindex.ai/api/mcp

Streamable HTTP, no credentials. Same six tools as the npm package.

Claude Code

claude mcp add --scope user mcpindex -- npx -y mcp-server-mcpindex@latest

Gemini CLI

gemini mcp add -s user mcpindex npx -y mcp-server-mcpindex@latest

Related MCP server: filesystem-mcp

Use it from Claude Desktop

Add to ~/Library/Application Support/Claude/claude_desktop_config.json:

{
  "mcpServers": {
    "mcpindex": {
      "command": "npx",
      "args": ["-y", "mcp-server-mcpindex@latest"]
    }
  }
}

@latest keeps you current: this is the advisory discovery server (not the in-path drift gate), so it carries no version pin — npx fetches the newest on your next host restart, no manual upgrade step.

Restart Claude Desktop. Then ask:

"Find me an MCP server that can read PDFs and write the contents to S3."

Claude calls recommend_mcp_for_task and returns the top 3 ranked servers with install commands.

Use it from Cursor

Add to .cursor/mcp.json:

{
  "mcpServers": {
    "mcpindex": {
      "command": "npx",
      "args": ["-y", "mcp-server-mcpindex@latest"]
    }
  }
}

Use it from Cline

Add to your Cline settings:

npx -y mcp-server-mcpindex@latest

Tools exposed

Agent-framework integration: advisory pre-invocation screen

check_tool_trust is the directory client integration surface (not the in-path mcpindex-gate). It lets agent frameworks (Composio, Mastra, LangChain, DSPy, raw LLM-tool-call loops) ask for an advisory screen verdict before dispatching a call. At v1 you will see REVIEW or UNVERIFIED — not a safety clearance.

Using Mastra? The sibling package @mcp-index/mastra ships this exact screen as a ready-made beforeToolCall hook - npm i @mcp-index/mastra, no wiring required.

Verdict contract (v1)

{
  "directive": "ALLOW" | "DENY" | "REVIEW" | "UNVERIFIED",
  "status":    "EVALUATED" | "PARTIAL" | "STALE" | "ERROR",
  "granularity": "description-level" | null,  // scope of a PARTIAL screen
  "dimensions": [
    { "id": "tool_safety", "verdict": "PASS", "severity": "INFO" }
  ],
  "expires_at": "2026-06-30T00:00:00Z",
  "honest_limits": [
    "conformance_monitored_not_enforced",
    "calibrated_false_v1",
    "advisory_deployment"
  ],
  "verdict_contract_version": "1.0.0",
  "server_id": "github",
  "tool_name": "create_pull_request",
  "source_url": "https://mcpindex.ai/api/v1/trust/tool/github/create_pull_request",
  "fetched_at": "2026-05-28T18:42:11.118Z"
}

The free-tier verdict ships directives + dimensions + freshness. Evidence quotes, LLM rationale, and chain history are paid-tier surfaces and intentionally omitted here.

Honest limits (pin these to your gate UI)

Every v1 verdict ships with these three caveats, and your gate SHOULD surface them on every dispatch decision:

1. conformance_monitored_not_enforced - publishers self-declare; mcpindex monitors drift but does not block at the network layer.

2. calibrated_false_v1 - dimension severities are not yet calibrated against real-world incident data.

3. advisory_deployment - the verdict is advisory; the agent (or human reviewing the agent) is the decision-maker.

History anchoring: OTS Bitcoin-anchored history; Bitcoin-finalized at N=6 confirmations (~1 hr); pending in ~10 min. Sub-window precision asserted, not proven.

Integration pattern (LangChain-style, direct LLM-tool-call convention)

import { Client } from '@modelcontextprotocol/sdk/client/index.js';
import { StdioClientTransport } from '@modelcontextprotocol/sdk/client/stdio.js';

const mcpindex = new Client({ name: 'gate', version: '1.0.0' }, { capabilities: {} });
await mcpindex.connect(new StdioClientTransport({
  command: 'npx', args: ['-y', 'mcp-server-mcpindex@latest'],
}));

// gateToolCall wraps any agent tool dispatch. Plug it in front of
// the LangChain / DSPy / Mastra / Composio tool-call hook.
async function gateToolCall({ serverId, toolName, invoke, askHuman }) {
  const res = await mcpindex.callTool({
    name: 'check_tool_trust',
    arguments: { server_id: serverId, tool_name: toolName },
  });
  const verdict = JSON.parse(res.content[0].text);

  // Pin the v1 caveats in the audit log no matter what.
  audit.log({ verdict, caveats: verdict.honest_limits });

  switch (verdict.directive) {
    case 'REVIEW':
      // Fail-CLOSED to human. Do NOT auto-execute on REVIEW.
      // At v1 this is the common screened outcome (semantic-only).
      return askHuman({ verdict, action: `${serverId}/${toolName}` });

    case 'UNVERIFIED':
      // No verdict on file (or upstream unreachable). Fail-CLOSED.
      // Recommend human review. Do NOT fail-open to invoke().
      return askHuman({
        verdict,
        action: `${serverId}/${toolName}`,
        note: 'No trust verdict on file. Human review required before first use.',
      });

    case 'ALLOW':
      // Reserved in the contract — not produced by the v1 public screen.
      // Keep the branch for future conformance-earned ALLOW; do not expect it today.
      return invoke();

    case 'DENY':
      // Reserved in the contract — not produced by the v1 public screen.
      throw new Error(
        `mcpindex denied ${serverId}/${toolName}: ${JSON.stringify(verdict.dimensions)}`,
      );

    default:
      // Unknown directive. Fail-CLOSED.
      return askHuman({ verdict, action: `${serverId}/${toolName}` });
  }
}

The load-bearing rule: never fail-open

If the verdict endpoint is unreachable, returns 404, times out, returns malformed JSON, or has no verdict on file yet for that server, check_tool_trust returns directive: "UNVERIFIED" + status: "ERROR". It never silently coerces to ALLOW. Your gate code SHOULD treat UNVERIFIED as "human review required", never as "looks fine, ship it."

status is telemetry about screen completeness, distinct from the directive trust decision: EVALUATED (full screen), PARTIAL (only part of the surface, e.g. description-level — see granularity), STALE (verdict past its freshness window), ERROR (unreachable / no verdict on file). A PARTIAL screen is never reported as EVALUATED.

This is tested. See test/trust.test.mjs.

Using the library directly (without MCP)

The trust client is also exported as a plain ES module:

import { checkToolTrust, assessServer } from 'mcp-server-mcpindex/src/trust.mjs';

const verdict = await checkToolTrust({
  serverId: 'github',
  toolName: 'create_pull_request',
});

if (verdict.directive !== 'ALLOW') {
  // Hand to a human, log, or block.
}

Backend

By default, calls go to https://mcpindex.ai. Override with MCPINDEX_API_BASE=... if you self-host.

The free tier is rate-limited to 60 req/min/IP. Paid keys are coming for higher throughput and the full evidence-bearing verdict (evidence quotes, LLM rationale, chain history).

Related packages

Three ways to bring mcpindex into an agent, for different surfaces:

Advisory screen vs drift gate: this package and @mcp-index/mastra ask mcpindex "has this tool been vetted?" (a network verdict). @mcp-index/sdk asks a different question locally: "did this tool's contract change since I pinned it?" Complementary, and none depends on another.

License

MIT.

Project

• Website: mcpindex.ai

• Methodology: mcpindex.ai/methodology

• Screen a server: mcpindex.ai/screen

• Guide: Find the right MCP server by task

• Source: github.com/mcpindex-ai

Unofficial. Not affiliated with Anthropic.