Cross Account Inventory Compare

Cross-Account Resource Inventory & Comparison

Routing behavior (endpoint ↔ region mapping, disambiguation rules, output labeling) is governed by the china-region-multi-account-routing skill; this skill assumes that routing is already in effect and focuses on how to query, correlate, and diff resources across both accounts.

When to use

Use this skill whenever the user's intent requires data from both China region accounts and a comparative or unified view of that data. Examples:

• "对比两个账号的 VPC CIDR"
• "两个中国区账号各自有几个 EC2 在跑"
• "北京账号有没有和宁夏同名的 security group"
• "哪些 S3 bucket 只在一个账号里存在"
• "两边的 IAM role 一致吗"

Do not use this skill when the user asks about a single explicitly-named account ("查宁夏的 EC2") — that is single-account inventory, not comparison.

Procedure

Step 1 — Identify the resource type and scope

Parse the user's request to extract:

• Resource type (EC2 instance, RDS DB, VPC, S3 bucket, IAM role, …)
• Scope (全部 / 运行中 / 某 tag / 某 name prefix / 某 region)
• Comparison key (name, tag Name, ID, ARN, configuration field)

If any of these is ambiguous, ask one clarifying question before proceeding.

Step 2 — Run the equivalent describe/list on both endpoints in parallel

Call the same AWS API on both aws-cn and aws-cn-2 MCP endpoints concurrently (not sequentially). Use the narrowest filter the user's request allows — avoid listing all resources of a type if a tag or name filter works.

Examples:

• EC2: aws ec2 describe-instances --filters Name=instance-state-name,Values=running
• RDS: aws rds describe-db-instances
• VPC: aws ec2 describe-vpcs
• S3: aws s3api list-buckets (plus get-bucket-location per bucket

since S3 is regional in China)

• IAM: aws iam list-roles (partition-wide, same per account)

Step 3 — Correlate across accounts

Match resources across the two accounts using the comparison key from Step 1. Partition the results into three buckets:

1. Only in aws-cn — present in Ningxia, absent in Beijing
2. Only in aws-cn-2 — present in Beijing, absent in Ningxia
3. In both — present in both accounts (matched by key)

For bucket 3, surface any configuration differences the user asked about (e.g., different CIDRs, different instance types, different tags).

Step 4 — Present the diff

Use a table when comparing configuration:

| Resource (by name) | aws-cn (Ningxia) | aws-cn-2 (Beijing) | |--------------------|------------------|--------------------| | prod-web-sg | 0.0.0.0/0:443 allowed | 0.0.0.0/0:443 allowed | | prod-db-sg | exists | missing |

Use grouped sections when listing disjoint sets:

### Only in aws-cn (Ningxia)
- i-0aaa... (t3.medium)
- i-0bbb... (t3.small)

### Only in aws-cn-2 (Beijing)
- i-0xxx... (t3.large)

### In both
(none, or list matched pairs)

Step 5 — Summarize findings

End the response with 1–3 sentences of interpretation: is the drift expected (e.g. DR-style asymmetry) or unexpected (e.g. missing resource)? Do not remediate — this skill is read-only analysis.

Things not to do

• Do not assume two resources with the same name are "the same" — they

are different AWS resources in different accounts. Say "matched by name" or "matched by tag X", never "the same resource".

• Do not silently drop resources from one side if the API fails on

that side. If aws-cn-2 returned an error, report "aws-cn-2: failed with " and still show aws-cn's data — do not pretend aws-cn-2 has no resources.

• Do not iterate sequentially on the two accounts when parallel is

possible. Users expect one round-trip latency, not two.

• Do not reformat IDs or ARNs when presenting — they need to be

copy-pasteable back into AWS CLI.

Examples

Input: "对比两个账号的 VPC CIDR"

Action: Parallel aws ec2 describe-vpcs on both. Extract CidrBlock and Tags[Name] per VPC. Match by tag Name. Output:

| VPC Name | aws-cn (Ningxia) | aws-cn-2 (Beijing) | |-----------|------------------|--------------------| | default | 172.31.0.0/16 | 172.31.0.0/16 | | prod | 10.0.0.0/16 | 10.1.0.0/16 | | dev | 10.10.0.0/16 | — (absent) |

Summary: "aws-cn-2 is missing the dev VPC; default overlaps (expected, both accounts use AWS's default). prod CIDRs are distinct (no overlap, safe to peer later if needed)."

Input: "两个账号各自多少个 running EC2"

Action: Parallel describe-instances --filters state=running. Output just counts plus instance IDs:

aws-cn (Ningxia):   3 running — i-0a, i-0b, i-0c
aws-cn-2 (Beijing): 1 running — i-0x

Input: "哪些 IAM role 只存在于宁夏账号，北京账号没有"

Action: Parallel aws iam list-roles on both. Compute set difference. Output:

### Only in aws-cn (Ningxia) — 2 roles
- mcp-pod-reader
- eks-node-group-extra

### Only in aws-cn-2 (Beijing) — 0 roles

### In both — 14 roles
(not listed unless requested)

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: aws-samples
• Source: aws-samples/sample-skills-for-AWS-Devops-agent
• License: MIT

Install and usage instructions live in the source repository linked above.