Bq assess

Skill aws-samples/sample-bigquery-to-aws-migration/skills/bq-assess

Assess BigQuery warehouses for migration to AWS. Triggers on: assess BigQuery migration, BigQuery to Redshift, BigQuery to AWS lakehouse, estimate migration complexity from BigQuery, analyze BigQuery warehouse for migration, migrate BQ to Redshift. Runs a 3-phase process: preflight environment check, scan via the bq-assess CLI, interpret the JSON assessment report and point the user to the generated HTML report. Do not use for: general BigQuery query tuning, Redshift administration, AWS-to-GCP reverse migrations, non-GCP warehouse assessments, Phase 2 migration execution (data load DML or Iceberg DDL deployment).From its SKILL.md

Install

npx -y skills add aws-samples/sample-bigquery-to-aws-migration --skill bq-assess

Assembled from the repository path, not quoted from the project. Check it against their README if it does not work.

One thing to look at

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SKILL.md

4.0 KB, as published. Nobody here has run it

bq-assess Skill

Philosophy

Read-only. No AWS commitment required. The assessment scans metadata and query logs; it does not provision resources or modify the BigQuery project.
Directional cost numbers. Savings estimates are conversation starters, not authoritative quotes. Always present them as approximate.
Query logs are optional. When logs are unavailable, confidence drops to LOW. Surface this explicitly — never hide the gap.
Defer architectural redesign. Schema changes, Iceberg partition/sort-order decisions, and migration execution belong to the user and the AWS account team, not this skill.

Definitions

"Load" = read the file with the Read tool and follow its instructions.
$REPORTS_DIR = output directory for CLI run (default reports/).

Prerequisites

Before running, the user must have:

bq-assess on PATH (or be willing to install it)
gcloud on PATH with ADC configured (gcloud auth application-default login)

State Machine

After every phase completion, consult this table to determine the next action. Each row maps to loading exactly one phase file.

Current state	Condition to leave	Next state	Phase file to load
`preflight`	Env checks pass AND `gcp_project` collected	`scan`	Load `references/phases/scan.md`
`scan`	CLI exits 0 AND landing JSON report exists	`interpret`	Load `references/phases/interpret.md`
`scan`	CLI exits non-zero	stay in `scan`	Follow Error Routing below
`interpret`	Summary presented AND HTML report path surfaced	terminal	Skill complete
any	User says "stop" or "cancel"	terminal	Exit immediately. Do not run the CLI or write files.

Entry points:

Any trigger phrase → load references/phases/preflight.md to begin the preflight phase.

Phase order is monotonic: phases advance strictly forward (preflight → scan → interpret). The only backward edge is error routing from scan back to preflight for credential failures. Cancellation exits from any phase.

Error Routing

When the CLI exits non-zero during the scan phase, match stderr against these patterns in order. On the first match, take the listed action.

Condition	Detection	Skill action
Missing `bigquery.jobs.listAll`	Not an error path. The CLI exits 0 and degrades silently. Detect after a successful run: `cost.estimate_basis` in the landing JSON contains `"No workload data"`	Do not report the run as clean. Follow "Workload Data Unavailable" in `references/phases/scan.md`: warn that cost confidence is reduced, then offer (1) grant `roles/bigquery.resourceViewer` and re-run, or (2) continue as-is. `--query-logs <path>` stays available if logs are already exported
Missing `bigquery.metadataViewer`	`ScannerError` from `validate_credentials()`	Route back to `preflight` auth step. Load `references/phases/preflight.md` and resume at authentication verification.
ADC expired	`google.auth.exceptions.RefreshError` in stderr	Route back to `preflight`. Show: `gcloud auth application-default login`
No tables found	CLI exits with `"No tables found. Nothing to assess."`	Prompt user to check the `--datasets` filter or verify the project ID is correct.
Unknown fatal	Non-zero exit, no pattern match above	Show stderr verbatim. Offer two choices: retry or cancel.