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

The annotations already declare readOnlyHint=true and destructiveHint=false, so the description adds some context beyond that by detailing the exact return fields and the meaning of overages_enabled. However, it does not disclose behavior like API rate limits or caching, but given the tool is simple and read-only, the description sufficiently supplements the annotations without contradiction.

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 long, tightly packed with useful information. It leads with the core purpose)Skip the exact fields returned, then provides practical usage guidanceches and an interpretation of the fields. Every sentence contributes significant value without redundancy.

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 that the tool has no parameters and a read-only nature, the description is fully complete. It explains the output fields and their semantics, and it mentions usage scenarios. The presence of an output schema further fills in structural details, so nothing essential is missing for an agent to invoke and interpret the tool 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 tool has zero parameterschers, so the description's job is to explain the output, which it does thoroughly. It defines what each field means and how to interpret them (e.g., the formula for remaining credits). This adds substantial value beyond the schema, which is empty.

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: it returns the organization's current image-credit usage, listing the specific returned fields. This is distinct from sibling tools that focus on creation, deletion, or listing of resources, making it clearly identifiable as a read-only utility.

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 explicitly says when to use it: 'to check capacity before rendering or explain a usage-limit error.' This provides clear context for use, and although it doesn't name specific alternatives, the purpose is so unique that the agent can infer it is the go-to for usage queries, distinguishing it from sibling tools that manage assets.

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