session_list

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

No annotations are provided, so the description must carry the burden. It states the tool displays a history list and allows confirming thread_id, which establishes it as a read-only operation. However, it does not disclose additional behavioral details such as ordering, pagination, or any required permissions, leaving some 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?

The description is two concise Japanese sentences that front-load the main purpose and then provide the key use case. Every sentence contributes valuable information without waste.

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, zero parameters, and the presence of an output schema, the description is nearly complete. It states the core functionality and links to the relevant sibling tool session_continue. It could mention return value specifics, but the output schema likely covers that, so the description suffices.

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 there are no parameter semantics to document. The schema trivially covers 100% of parameters, and the description adds no parameter-specific information. Baseline of 4 applies for zero-parameter tools.

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?

Description uses specific verb '表示' and resource 'Codexセッション（スレッド）の履歴一覧', clearly distinguishing it from sibling tools like session_continue. It also states the practical purpose of confirming thread_id, making the tool's function unambiguous.

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 mentions session_continue, implying this tool is the precursor for obtaining thread_id before continuing a session. It provides clear context for when to use it, though it does not explicitly exclude alternatives like list_codex_agents.

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