codex_send_message

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

Annotations are empty, so description carries burden. It labels as 'Compatibility write' and mentions delegation, but does not clarify that the call returns immediately (only hinted in parameter description) or other behavioral traits like error handling.

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?

Three sentences with front-loaded purpose and clear guidance. Minimal waste, but could be slightly more structured to include parameter or behavior highlights.

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 complexity (10 params, enums, output schema), the description covers purpose and a sibling alternative but omits parameter semantics, prerequisites (existing thread), and return value orientation.

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 10% (one parameter described). The description adds no parameter explanations, leaving the agent to infer from names and enums, which is insufficient for many parameters.

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 tool sends a message to an existing Codex thread and distinguishes from codex_submit_task by noting preference for durable long work. It uses specific verbs and resource references.

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?

Explicitly advises when to avoid this tool ('Prefer codex_submit_task...') and mentions delegation to durable queue in client mode, providing clear usage context.

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