Create a session

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

Annotations already declare readOnlyHint=false, idempotentHint=false, destructiveHint=false, and openWorldHint=true, so the safety/mutation profile is covered. The description usefully adds that the created session is a child of the current session and is for casting. It still omits session lifetime, auth/permission requirements, and what the response contains, so it adds moderate value beyond annotations.

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 opening line redundantly repeats the title ('Create a session') before restating it in the next sentence, which is wasted space. The core useful content (child session, casting) is front-loaded, and the operation/tag footer is compact, but the duplication keeps it at adequate rather than tight.

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 3-parameter, optional-param creation tool with annotations covering the safety profile and no output schema, the description covers the essential purpose and casting use case. Gaps remain around session lifetime, required permissions, and return behavior, making it minimally adequate rather than complete.

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 parameters (deviceOS, duration, deviceType) are considered documented, though their schema descriptions are trivial ('... (request body)'). The description adds no parameter-level meaning (e.g., duration units, valid deviceType values). Baseline 3 applies when the schema carries the load.

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 gives a specific verb+resource ('Create a session') plus meaningful scope detail: 'as a child to the current session' and 'used for casting.' This distinguishes it from the many other session tools. It stops short of explicitly naming siblings like update_session or end_session, keeping it from a 5.

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 casting context ('This endpoint is used for casting') implies when the agent should reach for this tool versus other session operations. However, there is no explicit when-not guidance and no named alternative (e.g., get_sessions, update_session, end_session). Usage is implied rather than stated.

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