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Verify agent actions against the system of record and get signed completion receipts.
About
Verify agent actions against the system of record and get signed completion receipts.
Security Report
This is a well-structured MCP server for outcome verification with proper authentication, minimal code attack surface, and permissions appropriately scoped to its purpose. The server requires a Postcept API key, validates all inputs with Zod schemas, and makes read-only or verification calls to external APIs. One minor concern: the API key is passed via Bearer token in HTTP headers, which is standard practice but requires HTTPS enforcement (not explicitly verified in code). Overall, the codebase demonstrates good security hygiene for a developer tools integration. Supply chain analysis found 3 known vulnerabilities in dependencies (0 critical, 3 high severity). Package verification found 1 issue.
6 files analyzed · 7 issues found
Security scores are indicators to help you make informed decisions, not guarantees. Always review permissions before connecting any MCP server.
Permissions Required
This plugin requests these system permissions. Most are normal for its category.
What You'll Need
Set these up before or after installing:
Environment variable: POSTCEPT_API_KEY
How to Install
Add this to your MCP configuration file:
{
"mcpServers": {
"io-github-postcept-mcp": {
"env": {
"POSTCEPT_API_KEY": "your-postcept-api-key-here"
},
"args": [
"-y",
"@postcept/mcp"
],
"command": "npx"
}
}
}Documentation
View on GitHubFrom the project's GitHub README.
@postcept/mcp
A Model Context Protocol server that exposes Postcept, outcome verification for AI agents, as MCP tools.
After an agent performs a high-risk action (a refund, a subscription
cancellation, a support-ticket resolution), it calls a verify_* tool to confirm
the action actually completed in the system of record (Stripe, Zendesk, and more)
and obtain a signed completion receipt. "done" becomes proof, not a claim.
The server is a thin wrapper over the live Postcept HTTP API. It holds no credentials of its own beyond your Postcept API key, and verification is read-only against your systems of record.
Configuration
| Variable | Required | Default | Notes |
|---|---|---|---|
POSTCEPT_API_KEY | yes | none | A Postcept API key (pcpt_sk_...) with verifications:write. |
POSTCEPT_BASE_URL | no | https://api.postcept.com | Point at a self-hosted or staging API. |
Create an API key in the Postcept dashboard under API keys.
Use with Claude Desktop / Claude Code
{
"mcpServers": {
"postcept": {
"command": "npx",
"args": ["-y", "@postcept/mcp"],
"env": { "POSTCEPT_API_KEY": "pcpt_sk_..." }
}
}
}
Tools
| Tool | Purpose |
|---|---|
verify_refund | Verify a claimed refund (exists, amount/currency/customer match, not duplicated). |
verify_cancellation | Verify a subscription was actually cancelled. |
verify_ticket | Verify a support ticket is in the expected state. |
get_verification | Fetch a past verification and its signed receipt by id. |
reconcile_verification | Re-verify a past verification against the live system of record. |
verified_completion_rate | Read the organization's Verified Completion Rate. |
Every verify_* tool accepts test: true to run against the deterministic
sandbox connector (excluded from your Verified Completion Rate), so an agent can
exercise the full flow without a live system of record.
A non-verified result (incomplete, duplicated, mismatched,
policy_failed) means the work is not done. Surface the gap and recover.
Advisory, by design
MCP puts the verification call in the agent's hands, which makes it the right integration for development, demos, and workflows where the agent's judgment is already trusted. It is advisory: an agent can skip the call, pass the wrong identifiers, or ignore the answer.
For consequential actions, enforce the decision outside the agent. The workflow
or orchestrator calls the Postcept API (or the SDK's guard()) itself and
branches on safe_to_claim_complete before anything customer-facing happens.
The agent then receives the allowed outcome instead of deciding it. Both
patterns use the same API and the same receipts, what changes is who owns the
branch.
Development
pnpm --filter @postcept/mcp build # compile to dist/
pnpm --filter @postcept/mcp typecheck
POSTCEPT_API_KEY=pcpt_sk_... node dist/index.js # stdio server
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