Resume Codex Agent

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

Annotations already cover the safety profile (readOnlyHint=false, idempotentHint=true, destructiveHint=false, openWorldHint=true). The description adds useful context that the tool 'loads and subscribes' to a thread, clarifying the state change involved. It does not disclose further behavioral details like event subscription semantics or failure handling, but given the annotations, it provides moderate additional transparency.

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 a single, well-structured sentence that front-loads the action and resource. Every word contributes meaning, with no redundant or vague phrasing – an example of good conciseness.

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 has 3 parameters (one nested), no output schema, and only partial schema descriptions, the description is too brief. It does not explain what resumeOptions does, what happens after resuming (e.g., can the agent immediately send messages?), or any prerequisites or side effects. An agent would need to inspect the schema closely and infer behavior, making the description incomplete for confident 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 only 33% – only resumeOptions has a description. The description itself does not explain threadId or label at all, even though threadId is required. With low coverage, the description fails to compensate, leaving the agent without clear meaning for the key 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 verb ('load and subscribe') and resource ('persisted Codex thread'), and the context ('after an MCP-server restart or from another Codex client') conveys that it resumes an existing thread, distinguishing it implicitly from sibling tools like agent_start or agent_fork. However, it does not explicitly name any alternative tools, which keeps it from a perfect score.

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 gives a clear usage context (after restart or from another client), which implies when to use this tool. It does not, however, explicitly state when not to use it or name alternative tools such as agent_start for starting new threads, so the guidance is implied rather than explicit.

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