aws_multi_region

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

Beyond annotations (which show readOnlyHint=false, etc.), the description adds critical details: partial failure is expected, duplicate regions are collapsed, returns regionCount for actual count, per-region error isolation, and validation details. No contradiction with annotations.

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 three sentences plus a list of examples. It front-loads the purpose and key behavior. While the examples are extensive and helpful, the description could be slightly more concise, but it remains well-structured and informative.

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?

Given 9 parameters, no output schema, and complex parallel behavior, the description covers return shape, concurrency, timeout, duplicate handling, validation, and provides usage examples. It fully equips an agent to invoke the tool correctly.

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%, and the description adds value by explaining the relationship to aws_call parameters (same shape), regions behavior (collapsing, validation), concurrency default, and timeout per region. The return structure is also described despite no output 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 clearly states 'Run the same AWS API operation across multiple regions in parallel.' It distinguishes from sibling aws_call by specifying the difference (regions array vs single region) and gives concrete examples like 'describe-instances across all our regions'.

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 description explicitly says 'Use for fleet-wide reads' and provides examples like 'list buckets in every region'. It implies when not to use (not for writes), but does not explicitly exclude alternative tools. However, the similarity to aws_call is noted, giving clear context.

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