Ground Truth

Stop your AI from being wrong.

Ground Truth lets AI agents verify claims, check live data, compare competitors, inspect APIs, and validate assumptions before acting.

MCP Cloudflare Workers

Live: https://ground-truth-mcp.anishdasmail.workers.dev

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What Ground Truth Verifies

Ground Truth helps agents check facts before they answer, recommend, or act.

Verification	What it checks	Example
Pricing claims	Pulls live pricing from product pages	"Does Stripe have a free tier?"
Competitor existence	Checks whether real alternatives show up in npm or PyPI	"Are there edge-first Prisma alternatives?"
API endpoints	Confirms a URL exists and responds	"Does this endpoint return 200?"
Package popularity	Compares package metadata side by side	"How do React and Vue compare right now?"
Market assumptions	Tests a hypothesis against live counts or responses	"Is this category still small?"
Support and policy claims	Checks public pages for language that supports or contradicts a claim	"Does this support policy actually apply?"

All results come from live data and are cached for 5 minutes for faster repeat checks.

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Why AI Agents Need Verification

Training data goes stale. Docs change. Pricing changes. Competitors appear. Endpoints break. Policies move.

Ground Truth gives agents a way to check before they commit:

• Before quoting a price, pull the live pricing page
• Before saying a competitor does not exist, search the live registry
• Before recommending an API, confirm the endpoint responds
• Before calling one package more popular, compare real package metadata
• Before repeating a policy, verify the language on the current public page

The result is simple: agents that are less confident for the wrong reasons and more reliable when it matters.

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Example Workflows

Verify a pricing claim

"Notion costs $8 per user per month for teams."

Use check_pricing on the live pricing page before repeating the number.

Check whether a competitor exists

"There is no good edge ORM alternative to Prisma."

Use estimate_market to search npm for edge orm and see what already exists.

Validate an API endpoint

"Use the OpenAI /v1/models endpoint to list available models."

Use check_endpoint before recommending it in docs, code, or support replies.

Compare package popularity

"Vue has overtaken React."

Use compare_competitors to compare live package metadata instead of guessing.

Test a market assumption

"There are fewer than 50 MCP tools on npm."

Use test_hypothesis with a count-based check and return the actual result.

Confirm whether a support policy applies

"AWS Business support includes 24/7 phone support."

Use verify_claim against the current AWS support page before treating that as fact.

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Free vs Pro

Free

Best for basic endpoint checks and limited verification needs.

• Only check_endpoint
• 100 requests per calendar month
• Tracked by Cloudflare client IP in production, or X-Anonymous-Client-Id for local/dev testing
• No signup or API key required

Pro

Built for agents that need higher limits and broader verification coverage.

• Requires X-API-Key
• Billing must be active
• Default quota of 5,000 requests per calendar month
• Monthly usage tracked per API key and tool
• Competitor comparison
• Claim verification
• Market checks
• Structured reports
• Priority response

View pricing

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API Examples

Direct API with curl

Direct HTTP calls to /mcp are session-based. Initialize once, keep the returned mcp-session-id, then call tools with that header.

SESSION_ID="$(curl -i -s -X POST https://ground-truth-mcp.anishdasmail.workers.dev/mcp \
  -H "Accept: application/json, text/event-stream" \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "method": "initialize",
    "params": {
      "protocolVersion": "2025-03-26",
      "capabilities": {},
      "clientInfo": {
        "name": "ground-truth-example",
        "version": "1.0.0"
      }
    },
    "id": 0
  }' | tr -d '\r' | awk '/^mcp-session-id:/ {print $2}')"

curl -X POST https://ground-truth-mcp.anishdasmail.workers.dev/mcp \
  -H "Accept: application/json, text/event-stream" \
  -H "Content-Type: application/json" \
  -H "Mcp-Session-Id: $SESSION_ID" \
  -H "X-API-Key: $GROUND_TRUTH_API_KEY" \
  -d '{
    "jsonrpc": "2.0",
    "method": "tools/call",
    "params": {
      "name": "check_pricing",
      "arguments": {
        "url": "https://stripe.com/pricing"
      }
    },
    "id": 1
  }'

JavaScript fetch

const initResponse = await fetch("https://ground-truth-mcp.anishdasmail.workers.dev/mcp", {
  method: "POST",
  headers: {
    "Accept": "application/json, text/event-stream",
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    jsonrpc: "2.0",
    method: "initialize",
    params: {
      protocolVersion: "2025-03-26",
      capabilities: {},
      clientInfo: {
        name: "ground-truth-example",
        version: "1.0.0",
      },
    },
    id: 0,
  }),
});

const sessionId = initResponse.headers.get("mcp-session-id");

if (!sessionId) {
  throw new Error("Missing mcp-session-id from initialize response");
}

const response = await fetch("https://ground-truth-mcp.anishdasmail.workers.dev/mcp", {
  method: "POST",
  headers: {
    "Accept": "application/json, text/event-stream",
    "Content-Type": "application/json",
    "Mcp-Session-Id": sessionId,
    "X-API-Key": process.env.GROUND_TRUTH_API_KEY,
  },
  body: JSON.stringify({
    jsonrpc: "2.0",
    method: "tools/call",
    params: {
      name: "compare_competitors",
      arguments: {
        packages: ["react", "vue"],
        registry: "npm",
      },
    },
    id: 1,
  }),
});

const result = await response.json();
console.log(result);

Free endpoint check

curl -X POST https://ground-truth-mcp.anishdasmail.workers.dev/mcp \
  -H "Accept: application/json, text/event-stream" \
  -H "Content-Type: application/json" \
  -H "Mcp-Session-Id: $SESSION_ID" \
  -d '{
    "jsonrpc": "2.0",
    "method": "tools/call",
    "params": {
      "name": "check_endpoint",
      "arguments": {
        "url": "https://api.github.com"
      }
    },
    "id": 1
  }'

Lightweight request checks for free access, blocked Pro calls, invalid keys, inactive billing, quota enforcement, and active Pro access live in test-usage-enforcement.sh.

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MCP Setup

If you use Claude Desktop, Cursor, or another MCP client, Ground Truth can plug in as a verification tool for your agent.

MCP stands for Model Context Protocol. It is the standard that lets AI apps call external tools.

Claude Desktop

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

{
  "mcpServers": {
    "ground-truth": {
      "url": "https://ground-truth-mcp.anishdasmail.workers.dev/mcp",
      "headers": {
        "X-API-Key": "gt_live_your_key_here"
      }
    }
  }
}

Cursor

Add this to .cursor/mcp.json in your project or ~/.cursor/mcp.json globally:

{
  "mcpServers": {
    "ground-truth": {
      "url": "https://ground-truth-mcp.anishdasmail.workers.dev/mcp",
      "headers": {
        "X-API-Key": "gt_live_your_key_here"
      }
    }
  }
}

Claude Code skill

If you want the same workflow without running a server, see claude-skill/.

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Use Cases

Support

• Verify a pricing claim before sending it to a customer
• Check whether a support policy applies before escalating
• Confirm an API endpoint exists before recommending it in a reply

Product

• Test whether a market assumption is true before writing a spec
• Check whether a competitor exists before framing a roadmap
• Compare package popularity before making a platform choice

Legal

• Confirm whether a support policy applies on a live public page
• Verify pricing or packaging claims before repeating them internally
• Check that a public terms or policy URL is reachable and current

Market research

• Compare competitor pricing across live pages
• Count category competitors before entering a space
• Validate positioning claims with structured checks

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Tool Reference

Tool	Tier	What it does
check_endpoint	Free	Checks whether a URL or API endpoint exists and responds
estimate_market	Pro	Counts packages in npm or PyPI for a search term
check_pricing	Pro	Extracts prices, plans, and free-tier signals from a page
compare_competitors	Pro	Compares packages side by side with live metadata
verify_claim	Pro	Checks whether live sources support or contradict a claim
test_hypothesis	Pro	Runs pass/fail tests against a live-data assumption

Full reference: API_USAGE.md

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Architecture

Ground Truth keeps the current Cloudflare Workers architecture:

• Runtime: Cloudflare Workers
• Storage: Durable Objects with SQLite for cache and usage logs
• API keys: Cloudflare KV
• Billing: Stripe Checkout and subscriptions
• Protocol: MCP
• Language: TypeScript

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Development

cd ground-truth-mcp
npm install
npx wrangler dev

Deployment notes live in SETUP.md.

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Documentation

• API_USAGE.md for API calls and tool arguments
• SETUP.md for deployment and billing setup
• claude-skill/ for the zero-deployment Claude Code version

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Support

• Email: [email protected]
• Issues: https://github.com/anish632/ground-truth-mcp/issues

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License

MIT — see LICENSE

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Made by Anish Das

Last updated: April 26, 2026