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

Annotations already declare readOnly/idempotent/non-destructive, so the safety bar is met structurally. The description adds genuine context beyond that: the brand budget is conditional ('when it has one') and the intended downstream behavior is to quote cost to the user. It stops short of noting any caching/freshness behavior, hence 4.

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?

Two sentences: the first front-loads the return contents, the second is the actionable directive. No filler or restated title text.

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 shape needn't be explained, annotations cover the safety profile, and the parameter is fully documented in the schema. The description supplies the one thing structure can't: when to call and what to do with the numbers.

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 100%, and the brandId field already documents its source (get_workspace/list_brands) and the single-brand omission rule. The description adds nothing about the parameter, so baseline 3 applies.

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?

Enumerates exactly what the tool returns (remaining credits, plan, per-brand monthly budget and usage, per-tool credit prices) rather than restating the name. No sibling in the list touches billing, and the description makes that scope unmistakable.

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?

Explicit directive: 'Call this before offering to generate anything, and quote the cost to the user.' That ties usage directly to the generation siblings (generate_design, generate_image, adapt_design) and tells the agent what to do with the result.

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