Assume Role

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

No annotations are provided, so the description carries the full burden of behavioral disclosure. It only restates the core action and does not explain that assuming a role changes the active session/credential context, that temporary credentials expire, or that caller permissions/trust policies may matter. For a security-sensitive operation, this is a meaningful gap.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a single, front-loaded sentence with no filler or redundant restatement of the tool name. It communicates the essential action and purpose immediately.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

The output schema exists and the input schema covers all parameters, so basic call construction is possible. However, with no annotations, the description leaves out important context about session behavior, credential lifetime, and how this differs from account switching tools, making it adequate but not complete.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the baseline is 3. The description adds no extra meaning about the parameters themselves; role_arn, external_id, duration_seconds, and session_name are already well documented in the schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description states a clear subject-verb-object: 'Assume an IAM role in another AWS account' and adds the cross-account purpose. This distinguishes it from sibling tools like select_profile or switch_account, which imply account switching rather than role assumption.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The phrase 'for cross-account access' gives a clear context for when this tool should be used. It does not explicitly name alternatives or list when not to use it, so it falls just short of the explicit when/when-not standard.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.