Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
git clone --depth 1 https://github.com/d-padmanabhan/agent-engineering-handbookWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/rules/d-padmanabhan/agent-engineering-handbook/412-aws-iam)<a href="https://agentmods.dev/rules/d-padmanabhan/agent-engineering-handbook/412-aws-iam"><img src="https://agentmods.dev/badge/rules/d-padmanabhan/agent-engineering-handbook/412-aws-iam.svg" alt="Measured on agentmods" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00032 | $0.03865 |
| Opus 5 | $0.00016 | $0.01932 |
| Sonnet 5 | $0.00006 | $0.00773 |
| Haiku 4.5 | $0.00003 | $0.00386 |
Grade A, and why
412-aws-iam scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 8d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 408 lines — stays where its author put it; the contents beside it link to each section on GitHub.
AWS IAM (Principals, Policy Evaluation, STS, SCPs, KMS)
Scope
This rule is AWS-specific and complements:
315-iam.mdc(identity and auth concepts across IAM/OIDC/SAML/PKI/PAM)410-aws.mdc(AWS engineering patterns)310-security.mdc(OWASP and general security)
Mental model: "Who am I?" vs "What can I do?"
- Authentication answers: who am I?
- Credentials and identity: IAM user access keys, federated user, or (most commonly) an assumed role session via STS
- Authorization answers: what am I permitted to do?
- Policy evaluation over: identity-based policies, resource-based policies, boundaries, session policy, and org guardrails (SCP)
IAM request evaluation (what AWS actually decides)
Think in four parts:
- Principal: the caller identity (often an STS assumed-role session)
- Action: the API operation (
s3:GetObject,kms:Decrypt,iam:PassRole, ...) - Resource: the ARN(s) the action applies to
- Context: condition keys (source VPC, principal tags, org ID, MFA, request region, ...)
Policy layers (common sources of confusion)
AWS authorization can include all of the below at once:
- Identity-based policies (attached to users/roles)
- Resource-based policies (S3 bucket policy, KMS key policy, Lambda permission, API Gateway resource policy)
- Permission boundary (limits the maximum permissions a role can exercise)
- Session policy (optional policy passed at
AssumeRoletime, further restricting the session) - SCP (Organizations) (limits maximum permissions in an account/OU; does not grant)
[!IMPORTANT] Explicit deny wins. A single applicable
Denyin any policy layer blocks the request.
Principal types (be precise)
Use the right terms in docs and debugging:
- IAM user: long-lived identity (avoid for automation)
- IAM role: identity intended to be assumed (workloads + automation)
- Assumed role session: the runtime principal after STS (
arn:aws:sts::ACCOUNT:assumed-role/RoleName/SessionName) - Federated user: temporary identity via federation mechanisms
- AWS account root principal:
arn:aws:iam::ACCOUNT:root(represents the account, not a human) - Service principal:
service.amazonaws.com(used in trust policies; not a KMS grant grantee)
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 8d ago First seen · 408 lines · 32 tokens per session scan A 27bb4312a04a
412-aws-iam is a cursor rule published in the GitHub repository d-padmanabhan/agent-engineering-handbook (16 stars, last pushed yesterday), licensed MIT. It adds 32 tokens to every session and 3,865 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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