aws_regional_availability

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

Annotations already declare readOnly, idempotent, non-destructive and open-world, so the safety profile is covered. The description adds genuinely new behavioral context — that filter names come from a catalog and can be discovered by omitting them — but says nothing about pagination behavior despite a nextToken parameter, nor about result freshness or cost of a lookup.

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?

Two tight sentences with zero filler, and the core purpose is front-loaded before the filter hint. The brevity is efficient rather than padded, though it borders on under-specified.

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?

Four parameters with 0% schema description coverage, a pagination token, a three-value enum and no output schema — the description is far too thin for this surface. An agent still cannot tell what resourceType values mean, whether multiple regions are batched, or how to continue past a page.

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 0%, so the description must carry parameter meaning and it largely does not. It explains filters (exact catalog names, omittable) but leaves regions, resourceType (what product/api/cfn actually select) and nextToken/pagination completely undefined; the enum values and the multi-region semantics are left to guesswork.

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?

"Check current regional support" gives a verb and a resource area, but never states what is supported (a product, API, or CloudFormation resource per the resourceType enum) or what is returned. Critically, it does not distinguish itself from the sibling aws_regions tool, which reads like a near-synonym to an agent choosing between them.

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 second sentence gives one real usage rule: omit filters when querying a single region to discover valid filter names. That is useful guidance but is scoped entirely to the filters parameter; there is no statement of when to use this tool instead of aws_regions or aws_knowledge_search, and no exclusions.

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