session_use

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

No annotations are provided, so the description bears full responsibility for behavioral disclosure. It reveals that the change is persisted to a file, which is useful context. However, it does not mention side effects, whether the operation overwrites an existing session, or how it interacts with leases. For a state-changing tool, this is minimal but not misleading.

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, efficient sentence that front-loads the core action ('Set the active session') and includes the key persistence note. Every word earns its place with no fluff or repetition.

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 tool that changes persistent state and has multiple related siblings, the description is underspecified. It does not explain what happens after setting the session, potential return values, or error conditions. The schema covers parameter details, but the overall behavior and selection context are missing, leaving an agent without enough information to confidently invoke the tool.

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%, and the schema already provides meaningful descriptions for all parameters, including the note about using a unique session name on a shared daemon. The tool description adds nothing about parameters beyond what the schema covers, so the baseline of 3 applies.

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 states a specific verb and resource ('Set the active session') and adds the persistence detail. However, it does not distinguish it from the sibling tool 'session_switch', which also deals with session switching. The agent might be unsure which one to pick based solely on this description.

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 no guidance on when to use this tool versus alternatives like session_switch or session_new. It does not mention any prerequisites, conditions, or exclusion criteria. An agent receives no help in choosing between session_use and its closely related siblings.

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