codex_explain

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

With no annotations, the description carries the full behavioral disclosure burden. It does convey useful behavior: Codex examines implementation, Git history, or conceptual design and returns comprehensive explanations. It does not explicitly state that the operation is read-only or mention access requirements, response format, or limitations, leaving some transparency gaps.

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 short sentences front-load the core purpose and then explain what Codex examines and what the user receives. There is no filler, and every clause adds meaningful information.

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 simple tool with three documented parameters, the description covers the key invocation details. It is incomplete in that it does not relate this tool to its siblings or clarify the expected shape of the returned explanation, and there is no output schema to fill that gap.

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%, so the baseline is 3. The description loosely reinforces the 'target' parameter by echoing its allowed categories (code, features, changes, Git context, concept), but it adds no new parameter-level detail beyond what the schema already provides.

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 opens with a specific verb and resource: 'Explain code, features, or changes.' It also names the investigation sources (implementation, Git history, conceptual design), making the tool's purpose clear. It does not explicitly distinguish itself from the sibling tools codex_consult and codex_review, so it falls short of a 5.

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 provides implied guidance: use this tool when a comprehensive explanation of code, features, changes, Git history, or design is needed. However, it never states when not to use it or how it differs from codex_consult and codex_review, so the routing decision is left to inference.

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