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

No annotations are provided, so the description must fully disclose behavioral traits. It does not mention any side effects (though 'check' implies read-only), authentication requirements beyond the API key, rate limits, or what happens on failure. It also does not state whether it accesses external systems or if it's local. The description is minimal and lacks depth.

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 extremely short, almost terse: 'Check credits + usage for a key.' It is front-loaded with the action and subject, and there is no fluff. However, it is so brief that it might be under-specified rather than appropriately concise.

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?

This is a simple tool with only one parameter and no output schema, so the description could easily be complete with a few more details. However, it lacks mention of the response format (credits and usage numerical values?), any prerequisites (such as having a valid key), or the significance of 'credits + usage' (e.g., for billing purposes). It is insufficient for an agent to know exactly what to expect.

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 compensate, but it simply says 'for a key' without explaining what format the api_key should be in, how it is used, or whether it is an API key for the service or a key for a specific resource. It adds minimal value over the schema, which just lists 'api_key' as a string.

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 verb and resource: 'Check credits + usage for a key.' This is specific enough to understand the basic purpose, but it does not distinguish from siblings beyond implying it's about account/credit status rather than file operations or ordering. It provides no details on what 'usage' means or what 'key' refers to specifically.

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 gives no guidance on when to use this tool versus the siblings. It does not mention that it is for checking balance/usage before performing other operations, nor does it explain the relationship to 'lynx_order' or 'lynx_signup'. There is no exclusion of when not to use it.

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