Check Codex readiness (free)

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

The description extensively discloses behavior beyond the readOnlyHint annotation: it is 'Free — no model call', fetches live data via a read-only call, and explains the meaning of each status ('blocked', 'limited', 'unknown', etc.) and edge cases like stale cache or different CODEX_HOME. This is consistent with the annotations and adds significant context.

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 long but well-structured: it opens with the core purpose, then provides usage timing, then walks through the complex rate_limit and blocked semantics. Every sentence adds value, and the front-loaded structure ensures the most important information is immediately visible.

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 the tool's complexity (multiple quota windows, stale vs live data, spend control), the description is thorough. It covers null windows, conservative available semantics, retry behavior for unknown, when to surface blocked to the user, and freshness indicators. An output schema exists, but the description still provides complete situational context.

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, so the baseline is 4. The description does not need to explain parameters, but it does explain what the tool reports (e.g., rate_limit block, spend_control_reached), which is helpful for understanding the output.

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: 'Check that the `codex` CLI is installed, authenticated, and a supported version, and report the resolved defaults.' It uses a specific verb ('check') and resource ('codex CLI'), and makes the tool's role distinct from sibling tools like codex_delegate or codex_dry_run by focusing on readiness and quota status.

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 gives explicit usage timing: 'Run it before your first paid call in a session to confirm setup, and again whenever a run fails with a setup error.' It also provides decision guidance for quota states (e.g., 'prefer to defer non-urgent Codex calls'). It does not explicitly mention when not to use the tool or name alternative tools, so it falls short of a 5.

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