codex_spawn

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

Annotations declare destructiveHint=true, openWorldHint=true and readOnlyHint=false, and the description corroborates with the critical behavioral warning that by default there is no sandbox and no approval, so Codex will directly modify files and run commands. It also discloses the detach semantics and the thread_id precondition (no still-running task on that thread), which annotations do not convey. It stops short of covering failure modes or rate/concurrency 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?

A single dense paragraph with no filler; the core capability and return value are front-loaded, followed by the sibling routing and then the sandbox warning. It is slightly over-packed with the five sibling name-drops in one breath, but every sentence carries operational 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 10-parameter mutating tool with no output schema, the description still explains the return value (8-digit id), how results arrive back to the session, the persistence option, and the default no-sandbox execution posture. Nothing an agent needs in order to call it correctly is missing.

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, but the description adds meaning beyond the schema: the detach flag's effect on turn blocking, the wait_s heuristic on which values yield an immediate result, and the constraint that a reused thread_id cannot have a running task. These are genuine additions rather than restatements of the schema text.

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?

States a specific verb+resource (dispatch a task to a Codex subagent) and the immediate return value (8-digit task id), plus the wait_s shortcut. It names the sibling tools codex_wait, codex_status, codex_steer and codex_interrupt, so an agent can distinguish this spawn tool from its siblings without opening another schema.

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?

Gives explicit when-to-use guidance: multiple concurrent dispatches are allowed and run in parallel in one resident process; task results auto-return to the session; thread_id is for continuing an old task's context but the thread must have no running task. It also surfaces the alternatives for monitoring/steering rather than leaving them to inference.

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