mcp

MCP runner

mcp/runner calls an external MCP server over stateless Streamable HTTP with the 2026-07-28 protocol. It opens a fresh connection for each Endly action. Tool calls are sent once; transport failures are returned without replaying a call.

The listTools action returns Tools and NextCursor. The call action takes name and structured arguments, and returns Result (the full MCP result), StructuredContent, Content, and IsError. A tool result with isError: true fails the Endly action while retaining the result in the service response. Set allowToolError: true on a call action when a workflow needs to inspect and publish an expected tool error; transport and protocol errors still fail.

pipeline:
  mcp-tool:
    action: mcp/runner:call
    init:
      url: https://example.com/mcp
      bearerTokenSecret: example-mcp-token
      timeoutMs: 30000
      name: describe
      arguments:
        entity: sample

bearerTokenSecret is a Scy resource reference or a root workflow credentialMap alias. The secret value is loaded at runtime and never included in the workflow response. Authenticated HTTP requires HTTPS, except for loopback HTTP. HTTP redirects are rejected when calling MCP endpoints.

For Scy OOB OAuth, set oauth instead of bearerTokenSecret:

oauth:
  configURL: /path/to/oauth-config.json|blowfish://default
  secretsURL: /path/to/basic-secret.json|blowfish://default
  authFlow: OOB
  scopes: [read]
  usePKCE: true

The OAuth config and Basic credentials must be stored as Scy resources. The runner passes these references to scy/auth/authorizer, receives an access token, and uses it only for the current MCP operation. OOB authorization may require interactive input. timeoutMs bounds authorization and the MCP call together. OAuth and bearer token references are mutually exclusive. No OAuth provider is contacted by the unit tests; they inject a local authorizer and mock HTTP server.

For negative invocation tests, allowProtocolError: true captures a JSON-RPC error as IsError: true and ProtocolErrorCode. It preserves only the numeric code; remote error messages/data are omitted because they may contain credentials. Transport failures still fail the action. The default remains false.

Native resources and skills use listResources, readResource, listSkills and getSkill. Listing accepts an optional cursor; reads accept uri. They share the same endpoint, SCY authentication and timeout options as tools. Read operations optionally capture redacted protocol errors with allowProtocolError: true. Skills listing never prefetches skill content.

pipeline:
  catalog:
    action: mcp/runner:listSkills
    url: $namespaceMCP
    bearerTokenSecret: $userToken
  skill:
    action: mcp/runner:getSkill
    url: $namespaceMCP
    bearerTokenSecret: $userToken
    uri: $catalog.Skills[0].Uri
  definition:
    action: mcp/runner:readResource
    url: $namespaceMCP
    bearerTokenSecret: $userToken
    uri: mcp://ns/sales