Steer active Codex turn

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

Annotations already declare readOnlyHint false, destructiveHint true, and idempotentHint false, so the agent knows this modifies state. The description adds context about the 'currently active turn' and the safety mechanism of expectedTurnId to avoid steering the wrong turn. Still, it does not explain failure modes or what happens if no active turn exists, so it provides only moderate additional transparency beyond the 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 two sentences long, front-loaded with the core action, and every word earns its place. It avoids repetition and includes both the primary function and an important usage hint without excess.

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 simplicity and the presence of detailed annotations, the description is adequate. It covers the key behavior and the critical safety parameter. A minor gap is that it does not explain return behavior or error conditions (e.g., what happens if no active turn exists), but since there is no output schema and the context is straightforward, this is not a significant omission.

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 coverage is 100%, so the baseline is 3. The description adds meaning for expectedTurnId by explaining its purpose ('prevent steering the wrong turn'), which goes slightly beyond the schema. However, it offers no additional context for prompt or threadId beyond the existing schema descriptions. Overall, the added value is marginal, so a 3 is appropriate.

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 appends guidance to the currently active turn, using the specific verb 'append' and resource 'guidance to active turn'. It also distinguishes itself from creating another turn, differentiating it from siblings like codex_send. The mention of expectedTurnId to prevent steering the wrong turn further clarifies its unique role.

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 implies when to use this tool: when you want to add guidance to an ongoing turn rather than starting a new one. The phrase 'without creating another turn' provides an exclusion, and the instruction to supply expectedTurnId when available gives practical guidance. However, it does not explicitly 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.