Account status

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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description adds value beyond them by disclosing credit costs (1 for a render, 2 for a screenshot) and feature-availability semantics that an agent cannot infer from annotations.

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?

Front-loaded with the two core questions the tool answers, followed by detail. The rhetorical 'How many credits are left, and what can this plan do?' framing is slightly verbose but effectively communicates scope in a short block.

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?

An output schema exists, so return-value structure need not be repeated, and the description covers credits, feature gating, and cost implications. Complete for a zero-parameter status tool, though it omits any mention of how often status changes or caching.

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 tool takes zero parameters, so there is nothing for the description to document and the baseline is 4. The credit-cost detail, while not a parameter, further informs invocation decisions.

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?

States a specific verb+resource ('Reports the credit balance plus which features are actually available') and enumerates the concrete facts returned (hi-res, screenshots, CDN expiry). This is clearly distinguishable from the sibling list/search/create/render tools.

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?

Gives a clear when-to-use trigger: 'Worth checking before a batch,' reinforced by the per-operation credit costs. It does not name an alternative tool or an exclusion, but the intent is unambiguous.

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