explain_key_usage

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

With no annotations, the description carries the burden of behavioral disclosure. It clearly states that no AWS credentials are required and enumerates the returned information: key type, permitted operations, compatible APC calls, and PCI considerations. The word 'Returns' implies a read-only operation, though an explicit no-side-effects statement would make it even stronger.

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 front-loaded with the trigger condition, followed by a compact return-value summary and a concise argument definition. There is no filler, and the example list earns its place because the parameter is an unconstrained string.

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?

For a simple one-parameter lookup tool with no output schema and no annotations, this description covers when to call, what to pass, auth requirements, and what to expect in the response. The main gap is not describing behavior for invalid or unknown key usage codes.

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%, but the description compensates by defining key_usage as a TR-31 key usage code and providing examples such as TR31_P0_PIN_ENCRYPTION_KEY plus a list of valid-looking codes. This is adequate for a single required parameter.

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 specific verb and resource: it explains TR-31 key usage codes and answers 'which key type should I use for X?' It gives concrete example codes and clearly distinguishes itself from the CRUD/list siblings by promising per-code explanatory details.

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?

It provides explicit trigger conditions: 'Call this whenever a TR-31 key usage code appears' or when someone asks which key type to use. It also notes that it works without AWS credentials. It does not explicitly name alternative tools or when-not-to-use, so it falls just short of a 5.

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