session_create

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

Annotations show readOnlyHint=false, indicating a write operation. The description confirms creation and adds critical behavioral context: the session is a plain UUID for gateway bookkeeping, not a provider-native session. This goes beyond annotations by clarifying the nature of the created session, though it does not cover potential side effects or permissions.

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 sentences long, each conveying essential information without fluff. The first sentence states the core action, and the second adds a crucial caveat. No wasted words.

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 and no output schema, the description adequately explains the purpose and key nuance. It could mention the return format (likely a session ID) for completeness, but the provided context is sufficient for most use cases.

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 coverage is 100%, so the description does not need to add parameter details. It does not provide any additional meaning beyond what the schema already describes (cli enum, description, setAsActive default). Baseline 3 is appropriate.

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 creates a 'gateway session record for a provider' and distinguishes it from 'provider-native session' with a specific note about Codex UUIDs. The verb 'create' is specific and the resource 'session record' is well-defined, differentiating from sibling tools like session_delete or session_list.

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 provides clear context about what the tool does (gateway bookkeeping) and explicitly cautions that Codex resume needs a real Codex UUID, implying when not to use it. However, it does not explicitly list alternative tools or conditions for using this versus other session operations.

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