State the outcome
Define a concrete result before or after an action, with an explicit subject and deadline if needed.
Outcome verification for AI agents
The tool returned success. Did the world change?
Postcondition declares the intended result, observes the outside world through constrained read-only verifiers, and returns an honest verdict: satisfied, violated, or unknown.
npx -y postcondition-mcp serve
POSTCONDITION / RECEIPT● OBSERVED
“Version 0.1.0 is visible in the public npm registry.”
- verifier
- npm.version_exists
- evidence class
- externally_observed
- expected
- 0.1.0
- observed
- 0.1.0
- verdict
- SATISFIED
receipt e72168e33d153f69…
53automated tests
7MCP tools
5verifier kinds
20 / 22 / 24Node versions in CI
The missing step
Execution is an event. Completion is a claim.
A successful tool response proves that a call returned. Postcondition asks for a separate, observable statement about the world after the action.
Use any tool
Postcondition does not become another orchestrator. Your existing MCP tool, CI job, human, or script performs the work.
Check independently
A narrow verifier reads file, HTTP, Git, or npm state without executing arbitrary shell commands.
Keep the honest verdict
Satisfied, violated, or unknown — with evidence class, digest, timestamp, and a link to the previous receipt.
Live public observation
Do not trust this page. Ask the registry.
This browser demo reads npm's public registry directly and compares the observed version with the expected one. The installable product adds durable contracts, evidence classes, SQLite persistence, and a receipt chain.
registry.npmjs.org/postcondition-mcpREADY
expected
observed
verdict
evidence SHA-256
Constrained verification surface
Narrow observers instead of arbitrary commands.
The built-in verifier set is intentionally small. Every unsupported or unreachable condition resolves to unknown instead of manufactured success.
Filesystem state
Existence, absence, size, SHA-256, contained text, and JSON pointer equality.
Remote GET state
Status, text, and JSON values with redirect, timeout, response-size, and private-network guards.
Repository state
Branch, clean tree, HEAD, tag, and local remote-tracking containment through fixed argument sets.
Registry state
Published versions and dist-tags observed through the registry's public API.
Explicit attestation
Human or agent statements stay labelled and are never upgraded to external proof.
Evidence honesty
Observation and attestation are not the same thing.
| Evidence class | Meaning |
|---|---|
| externally_observed | A remote HTTP or npm endpoint was read independently. |
| configured_verifier | A constrained local file or Git check ran. |
| manual_attestation | A human supplied the result. |
| self_attestation | An agent supplied its own result. |
Strong boundary. Honest limits.
- No arbitrary shell verifier, action execution, account, telemetry, or required cloud service.
- HTTP is GET-only and blocks loopback, private, link-local, and reserved targets by default.
- The local hash chain detects mutation but is not yet externally signed notarization or cryptographic non-repudiation.
- Git remote containment reads locally fetched tracking refs and does not silently contact or mutate the remote.
One coherent trust stack
Soul remembers why. Postcondition checks what changed.
Postcondition grew from a repeated design principle across Christian Bucher's Soul and Miguel systems: autonomy should carry evidence, permission boundaries, corrections, and observable outcomes. The public repository is a clean implementation — not an export of personal memory or private session logs.