Thanks for sharing the snippet — the error is due to step structure. In Prefect 3.x, each step must be a single-key mapping where: - The single key is the fully qualified function path - Optional reserved keys like

id

,

requires

, and

if

live alongside that key (not inside the function’s parameter dict) In your YAML,

requires

is nested under the function’s parameters. That causes the step validator to see unexpected keys and raise:

ValueError: Step has unexpected additional keys: prefect_aws.deployments.steps.pull_from_s3

Here’s a corrected version:

pull:
  - prefect_aws.deployments.steps.pull_from_s3:
      bucket: my-bucket
      folder: my-folder
      credentials: "{{ prefect.blocks.aws-credentials.my-bucket-credentials }}"
    requires: prefect-aws

  - prefect.deployments.steps.run_shell_script:
      script: pip install -e ./python-flows

Notes: - Move

requires

out to the same level as the step (as shown). - For AWS credentials, the block type is typically

aws-credentials

, so use

{{ prefect.blocks.aws-credentials.<your-block-slug> }}

. Your

prefect.blocks.s3...

path looks off. - Double-check the path in your

pip install -e

command. If the S3 contents land under

my-folder

, you may want

pip install -e ./my-folder/python-flows

unless your repo layout differs. Refs: - prefect.yaml structure - Pull steps API - Utility steps API If you’re still seeing the error after moving

requires

, please paste the full

pull:

section and confirm your Prefect version so I can help further.

Got it — thanks for clarifying you’re on Prefect 2.20.17. In 2.x, the step syntax is slightly different than 3.x. In Prefect 2.x: - Each step is a list item where the single key is the step’s import path. - The values under that key include both the step’s parameters and the optional

id

and

requires

. Your structure is almost there; two things to fix/check: 1) Use the AWS credentials block type (

aws-credentials

), not

s3

, for the

credentials

field. 2) Ensure indentation is correct and each step is its own list item. Here’s a corrected 2.x example:

pull:
  - prefect_aws.deployments.steps.pull_from_s3:
      id: pull_code
      requires: "prefect-aws>=0.3.4"
      bucket: "my-bucket"
      folder: "my-folder"
      credentials: "{{ prefect.blocks.aws-credentials.my-bucket-credentials }}"

  - prefect.deployments.steps.run_shell_script:
      script: "pip install -e ./python-flows"
      stream_output: true

Why you saw that error - Prefect raises “Step has unexpected additional keys: prefect_aws.deployments.steps.pull_from_s3” when a step’s mapping isn’t shaped as “one function key + its parameters (plus optional id/requires)”. This often happens due to indentation or mixing multiple step keys under one list item. Double-check that both steps have their own dash and that there are no tabs or misaligned spaces. Docs for Prefect 2.x - Steps + YAML: https://docs-2.prefect.io/latest/guides/prefect-deploy/ - AWS steps: https://docs-2.prefect.io/latest/integrations/prefect-aws/deployments/steps/ If it still errors, can you paste your full

pull:

section (as it appears in the file) and confirm the

prefect-aws

version installed in the runtime environment?