What this API key can do

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

With no annotations provided, the description carries the full burden. It discloses that the call is free, spends no quota or credits, is never refused for over quota, works even after a 429, and that any valid key may read its own entitlements. This goes beyond basic expectations and covers cost, failure modes, and access control.

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 but each sentence earns its place: first lists returns, second gives usage rationale, third covers cost and access. It is front-loaded with the most important information and contains no filler.

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 no output schema exists, the description adequately describes the returned data. It also covers when to call, cost, reliability, and authorization, making it complete for a zero-parameter informational tool.

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?

The input schema has zero parameters and schema coverage is 100%, so the baseline is 4. The description does not need to explain parameters, but it enriches understanding by detailing the return fields (plan, scopes, quota, credits, kit slots), which adds semantics beyond the empty 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 the tool returns the current API key's plan, scopes, quota, credit balance, and saved-kit slots. This is a specific verb+resource (read entitlements) and is distinct from sibling tools like list_mockup_jobs or get_kit_version. The title 'What this API key can do' reinforces the purpose.

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?

Provides explicit when-to-use guidance: 'Call it before promising a user something the key cannot deliver.' It also explains the alternatives (encountering 403, 429, 402 errors) and states the tool is safe to call first, giving a clear decision rule.

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