Read Codex thread

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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, covering the safety profile. The description adds a substantive behavioral detail: the bridge denies threads outside CODEX_ALLOWED_ROOTS, which is not visible in annotations. This informs the agent about potential authorization failures and scoping limits.

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 sentences with no filler. The main purpose is front-loaded in the first sentence, and the second sentence provides a crucial constraint. Every word contributes to understanding the tool.

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, strong annotations, and full parameter schema coverage, the description is mostly complete. It does not describe the return value format, but with no output schema, that is a gap; however, the name and the includeTurns parameter reasonably convey what is returned. The authorization constraint adds essential context for operational use.

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% for both parameters, so the structured schema already defines threadId and includeTurns. The description adds no additional meaning beyond what the schema provides, such as the distinction between compact and full turn views, which is already in the schema. Baseline 3 is appropriate when schema covers parameter semantics.

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 action ('Read') and the resource ('a persisted authorized Codex thread'), immediately distinguishing it from sibling tools like codex_list_threads (list threads) or codex_status (status check). The scope is well-defined with the authorization constraint, making the tool's purpose 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 implies usage for reading a specific thread's contents, but it does not explicitly differentiate from alternatives like codex_status or codex_list_threads. The mention of CODEX_ALLOWED_ROOTS is a constraint on valid inputs rather than guidance on when to choose this tool over others. Use is implied rather than clearly instructed.

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