Get Codex usage

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

Annotations already declare this as safe and idempotent. The description adds meaningful behavioral context by specifying the exact data it returns (plan, usage, reset window, credits, limit state), which goes beyond the generic 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?

The description is a single, front-loaded sentence beginning with the practical usage context. Every clause adds value by naming the accessible information, with no filler or redundant content.

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?

For a zero-parameter, read-only tool with an output schema and annotations, the description is complete. It covers why, when, and what to expect, making it fully sufficient for an agent to select and invoke 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 parameters, and the description correctly focuses on the tool's function rather than parameter details. Since there are no inputs to explain, the description fully satisfies parameter semantics without additional explanation.

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 uses a specific verb ('read') and clearly identifies the resource and scope: current Codex plan, remaining usage, reset window, credits, and limit state. It also provides the timing for use, which further distinguishes it from the sibling tool countdown_advise_work.

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 states when to use this tool: 'before large or multi-stage work.' It gives clear context, though it does not mention when not to use it or compare with countdown_advise_work as an alternative.

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