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

With no annotations, the description fully discloses behavior: it uses the API key from the current request, standardizes the return fields (total, remaining, used), and enforces a security boundary by not allowing passthrough of apikey parameters and not returning the full key. This gives clear expectations of side effects and constraints.

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 concise, consisting of two clear sentences that cover purpose, input constraint, behavior, output format, and security. It is well-structured and free of unnecessary details.

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?

Even without an output schema, the description specifies the standardized return fields (total, remaining, used) and explains the security boundary. This provides sufficient information for an agent to understand what the tool returns and how to use it correctly.

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 schema has zero parameters, and the description explicitly states 'no business input parameters', clarifying that the tool relies on the request's API key. This goes beyond the empty schema and prevents any confusion about expected inputs.

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's purpose: to query the total quota, used amount, and remaining amount of the API Key for the current request. This is distinct from all sibling tools, which focus on customers, sessions, tags, and messages.

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 explains that the tool has no business input parameters and uses the current request's API key, but it does not explicitly mention when to use this tool versus alternatives, or provide any comparison to sibling tools. The usage context is implied but not directly stated.

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