Aws Reserved Offerings

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 one genuinely useful behavioral note — results are '(capped)' — and reinforces the no-purchase guarantee, but never says how large the cap is or what happens when it is hit, so the disclosure of truncation behavior is incomplete.

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?

A single front-loaded sentence naming the API operation, the term options, the three returned facts, and the safety caveat, with zero filler. Slightly dense phrasing, but every clause carries information.

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?

With an output schema present and full parameter documentation, the description only needs to convey scope and intent, which it does for a three-parameter read tool. The remaining gap is the unexplained '(capped)' limit, which an agent would want quantified before relying on completeness of results.

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 schema already documents node_type, engine and the nullable region with its AWS_REGION default and pattern. The description only restates that offerings are keyed by node type and engine and says nothing about region, so it adds little beyond structured data — baseline 3 applies.

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?

States a specific verb and resource ('DescribeReservedCacheNodesOfferings') plus the concrete payloads it returns: 1y/3y offerings for a node type and engine, the count of running nodes not covered by a reservation, and the cheapest offering per term. An agent can tell it is an offerings/coverage-gap read rather than a reservation listing. It does not explicitly name the sibling that lists existing reservations (aws_reserved_nodes), so it stops short of 5.

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?

'Never purchases anything' functions as a when-not caveat, steering agents away from treating this as a buying or mutating call. However, there is no explicit guidance on when to prefer this over aws_reserved_nodes or aws_cost_overview, so the routing is only implied by the stated contents.

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