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

With no annotations, the description carries the full disclosure burden; it makes clear this is a read of account state (plan, credits, upgrade URL) rather than a mutation. It does not say whether the call itself consumes a credit, whether it requires authentication, or what the denial condition looks like, and the bracketed '[Free · 1 credit]' tag is ambiguous about cost.

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?

Three short sentences, front-loaded with what the tool returns before the trigger condition. The trailing '[Free · 1 credit]' tag is cryptic and slightly undercuts an otherwise clean, waste-free description.

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?

Zero params, no output schema, and no annotations mean the description is the only specification, and it covers the return contents and the call trigger. Minor gaps remain around authentication and whether the call is metered, but nothing an agent needs to invoke it correctly is missing.

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?

There are zero parameters, so there is nothing to disambiguate and the baseline applies. The description adds no parameter meaning because none exists.

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 names the concrete returns: plan, credits remaining this month, and upgrade URL. That is more specific than the bare name 'account' and tells an agent exactly what payload to expect, though it does not explicitly contrast itself with any sibling tool.

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?

'Call this when a request was denied' is an explicit, actionable trigger condition that an agent can pattern-match on. It lacks a stated when-not (e.g., use proactively before hitting a limit), but for a zero-parameter status tool this is close to sufficient guidance.

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