@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_..." }
}
}
}
| 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
pnpm --filter @postcept/mcp typecheck
POSTCEPT_API_KEY=pcpt_sk_... node dist/index.js