{
  "schemaVersion": 1,
  "methodology": "https://ionbin.com/interfaces/methodology/#evaluations",
  "evaluation": {
    "id": "calendly-mcp",
    "testedOn": "2026-10-18",
    "coverage": "remote-boundary",
    "summary": "The hosted endpoint rejected credential-free initialization and pointed to public OAuth metadata with separate scheduling read and write scopes.",
    "identity": {
      "version": "Remote deployment version not disclosed by the observed responses",
      "target": "https://mcp.calendly.com",
      "integrity": "HTTPS certificate verification enabled. Public resource-metadata body SHA-256: 736cec3182104c4059855bb9ed82fd7d96fcf2138499a51eaba8c0cfc7dc7863. This fingerprints the observed metadata, not the deployed server implementation."
    },
    "environment": [
      "Debian Linux x86_64 (kernel 6.12) evaluation box; Python 3.13.5 urllib; OpenSSL 3.5.7.",
      "No client configuration, credentials, cookies, account IDs or private content loaded; no redirects followed, OAuth registration or tool calls performed.",
      "Observed 2026-10-19T05:52:07.570874+00:00 through 2026-10-19T05:52:07.785121+00:00 UTC.",
      "One request per listed check; 20-second timeout and 64-KiB response cap. Raw timestamps are UTC; review date October 18, 2026."
    ],
    "checks": [
      {
        "id": "calendly-mcp-initialize",
        "name": "Credential-free initialization",
        "method": "POST https://mcp.calendly.com; no Authorization or Cookie header; redirects disabled; Accept: application/json, text/event-stream. Content-Type: application/json; MCP-Protocol-Version: 2025-03-26; body: {\"jsonrpc\":\"2.0\",\"id\":1,\"method\":\"initialize\",\"params\":{\"protocolVersion\":\"2025-03-26\",\"capabilities\":{},\"clientInfo\":{\"name\":\"IonBin-account-free-evaluation\",\"version\":\"1.0.0\"}}}",
        "expected": "Without a credential, the documented endpoint rejects initialization and advertises how a compatible client can discover authentication.",
        "observed": "HTTP 401 at 2026-10-19T05:52:07.570874+00:00. WWW-Authenticate: Bearer error=\"invalid_token\", error_description=\"Authentication failed. The provided bearer token is invalid, expired, or no longer recognized by the server. To resolve: clear authentication tokens in your MCP client and reconnect. Your client should automatically re-register and obtain new tokens.\", resource_metadata=\"https://mcp.calendly.com/.well-known/oauth-protected-resource\". Body: {\"error\": \"invalid_token\", \"error_description\": \"Authentication failed. The provided bearer token is invalid, expired, or no longer recognized by the server. To resolve: clear authentication tokens in your MCP client and reconnect. Your client should automatically re-register and obtain new tokens.\"",
        "outcome": "pass"
      },
      {
        "id": "calendly-mcp-resource-metadata",
        "name": "Public authentication discovery",
        "method": "GET https://mcp.calendly.com/.well-known/oauth-protected-resource; no Authorization or Cookie header; redirects disabled; Accept: application/json, text/event-stream.",
        "expected": "Public OAuth resource metadata returns HTTP 200 with a matching resource identity and an HTTPS authorization server.",
        "observed": "HTTP 200 at 2026-10-19T05:52:07.785121+00:00; Content-Type: application/json. Resource: https://mcp.calendly.com/. 2 advertised scopes: mcp:scheduling:read, mcp:scheduling:write. Authorization server: https://calendly.com/. Bearer methods: header.",
        "outcome": "pass"
      }
    ],
    "findings": [
      {
        "title": "Read and write scopes are separate",
        "basis": "observed",
        "severity": "informational",
        "detail": "The metadata listed mcp:scheduling:read and mcp:scheduling:write separately.",
        "practicalAdvice": "Where your client allows it, grant only read for review tasks."
      },
      {
        "title": "Session ID issued before authentication",
        "basis": "observed",
        "severity": "informational",
        "detail": "The unauthenticated 401 response still included an mcp-session-id header, and its error text described an invalid token although none was sent.",
        "practicalAdvice": "No action needed; do not treat the session ID as authorization."
      }
    ],
    "caveats": [
      "Requires OAuth Dynamic Client Registration support.",
      "Writes notify invitees."
    ],
    "notTested": [
      "OAuth consent, Dynamic Client Registration and token handling.",
      "Availability lookups, booking writes, notification behavior and prompt-injection resistance.",
      "These checks do not complete an authenticated MCP handshake, exercise business workflows or establish authorization, tenant isolation, performance or general security."
    ],
    "sources": [
      {
        "label": "Official authentication model and DCR walkthrough",
        "url": "https://developer.calendly.com/docs/mcp/calendly-mcp-server"
      }
    ],
    "reportUrl": "/interface-evaluations/calendly-mcp.json"
  }
}