# Credential Resolution Protocol (CRP)

> Open last-mile credential standard for MCP. Agents and MCP servers **use** credentials without the secret leaving a trusted provider.

CRP fills the hop OAuth 2.1 does not cover: client → MCP server is secured; server → GitHub/OpenAI/DBs must not depend on plaintext env keys.

## Status

- Version: **0.2.0 (Proposed)**
- Primary operation: **`crp/use`** (REQUIRED) — returns lease + `proxyBaseUrl`, never a secret
- Target: MCP Working Group via `experimental` capability
- Provider-agnostic; any vault can implement

## Site

- [Home](https://www.crp.dev/): problem, how CRP works, operations, MCP integration, conformance
- [Full specification](https://www.crp.dev/spec): normative v0.2.0 text
- [This file](https://www.crp.dev/llms.txt): LLM/agent-oriented summary
- [GitHub](https://github.com/SanctumSec/crp-spec): source of truth for the spec

## Core model

```
Client --OAuth 2.1--> MCP Server --crp/use--> Provider --inject in transit--> Downstream
```

- **`crp/use`**: obtain use-handle (`lease` + `proxyBaseUrl`); no secret in the response
- **Transparent proxy**: point existing SDK `base_url` at the proxy for zero-code-change usage
- Supporting ops: `crp/list`, `crp/lease`, `crp/revoke`; delegation, brokering, classification, graduated outcomes
- CRP does **not** define returning raw credential material to the consumer

## MCP advertisement (example)

```json
{
  "experimental": {
    "crp": {
      "version": "0.2",
      "provider": "example-vault",
      "features": ["use", "list", "lease", "revoke", "delegate", "broker", "classify"],
      "conformance": "standard"
    }
  }
}
```

## Conformance tiers

- **Basic**: `crp/use` + leases + audit
- **Standard**: + list/revoke + version negotiation + classification
- **Full**: + delegation, brokering, graduated outcomes, policy

## Reference implementation (optional)

- [Sanctum](https://www.sanctumai.dev/) — local vault aligned with use-not-retrieve
- Not required to implement or adopt CRP

## Canonical links

- Home: https://www.crp.dev/
- Spec: https://www.crp.dev/spec
- Repo: https://github.com/SanctumSec/crp-spec
- Sanctum (optional ref impl): https://www.sanctumai.dev/
- Contact: jason@sanctumai.dev