SAM Doctor

ERROR REFERENCE

The endpoint rejected the requested API action

AWS did not recognize the operation at the endpoint that received the request. Check the operation, service endpoint, SDK or CLI version, and Region before changing permissions.

WHAT IT MEANS

The action is unknown or invalid here

An error occurred (UnknownAction) when calling the GetTemplateSummary operation: Action is not supported

The endpoint rejected the operation itself. This can be a misspelled or newly introduced API action, a client using the wrong API version or Region, a request sent to the wrong service endpoint, or a local AWS emulator that has not implemented the operation. It is not evidence of an IAM denial.

NEXT CHECK

Verify the operation and endpoint together

  1. Read the exact operation and service. Copy the action name from the evidence line and identify whether the caller is using the real AWS endpoint or a local emulator.
  2. Compare with the current API. Check the service's API reference, selected Region, and SDK or CLI version. Upgrade the client or use the supported operation when the action was introduced after the version in use.
  3. Check emulator support when applicable. A local emulator may report an AWS-shaped error for an action it has not implemented; use a supported substitute or run this step against the real service before changing deployment code.

AUTOMATE THE TRIAGE

Keep the check in your normal workflow

SAM Doctor recognizes the AWS UnknownAction and InvalidAction operation markers with low confidence and keeps the advice investigative. Runs locally; no AWS access, no log upload. 

python -m pip install sam-doctor
sam-doctor diagnose deployment.log --format markdown

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