Fork Codex Agent

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

Annotations already convey the mutation profile (readOnly=false, idempotent=false), and the description adds meaningful context: the fork is 'independent' and an optional prompt triggers immediate work. This helps the agent anticipate that forking can spawn active work, though details like whether the fork returns immediately or waits are not disclosed.

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 tightly written sentences, with the core operation front-loaded and the optional prompt behavior stated second. Every word contributes; there is no filler or repetition of schema details.

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 tool with six parameters, no required fields, and no output schema, the description is too sparse to guide correct invocation. It omits how the source agent/thread is selected, what label means, and what the caller should expect as a result of the fork.

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 only 33%, and the description does not meaningfully clarify the six parameters. 'Optional prompt starts work immediately' touches on the prompt parameter, but the crucial sourceAgentId vs sourceThreadId distinction, label purpose, and forkOptions/turnOptions semantics are left unexplained.

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 uses a specific verb ('Branch') and names the exact resource ('a managed agent or persisted Codex thread') plus the outcome ('a new independent worker'). This clearly distinguishes agent_fork from lifecycle siblings like agent_start or agent_resume.

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 establishes clear context: use this when you already have a managed agent or persisted Codex thread to branch, and include an optional prompt to start work immediately. It does not explicitly name alternatives or state when not to use the tool, but the source precondition is clear.

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